Railroad electrification in the United States
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Railroad electrification in the United States began at the turn of the 20th century and comprised many different systems in many different geographical areas, few of which were connected. Despite this situation, these systems shared a small number of common reasons for electrification.
Most of the systems discussed in this article are either no longer electrified, or are now part of the Northeast Corridor and Keystone Corridor systems used by Amtrak and several commuter rail lines. One exception is the Black Mesa and Lake Powell Railroad, an isolated system hauling coal from a mine to a power plant. Most mass transit, streetcar and interurban systems electrified very early—many from the beginning—but are not within the scope of this article.
- 1 Impetus for electrification
- 2 Overview of electrification in the U.S.
- 3 History of electrification projects in the United States
- 3.1 Smoke abatement
- 3.2 Tunnels
- 3.3 Mountainous Terrain
- 3.4 Traffic Density
- 3.4.1 Amtrak
- 3.4.2 Boston, Revere Beach and Lynn Railroad
- 3.4.3 Erie Railroad (Rochester Division)
- 3.4.4 New York, New Haven and Hartford Railroad
- 3.4.5 Pennsylvania Railroad
- 3.4.6 Rock Island & Southern Railway
- 3.4.7 Spokane & Inland Empire Railroad
- 3.5 Suburban Commuter Operations
- 3.6 Freight operations
- 4 See also
- 5 Footnotes
- 6 References
Impetus for electrification
The common reasons for electrification in the United States include:
Laws banning steam locomotives (smoke abatement)
A number of municipalities passed laws in the early part of the 20th century forbidding steam locomotives from operating within city limits, after some bad accidents caused by the awful conditions of visibility in smoke and steam-filled tunnels and cuttings. The most prominent of these laws was for New York City in 1903 (effective 1908).
An extensive study was also undertaken in Chicago of the problems of smoke and the feasibility of electrification as a solution.
Long, deep tunnels provide poor ventilation for steam locomotives, to the point where crews had to wear oxygen masks to avoid asphyxiation. The ventilation problem also limited the frequency of trains through these tunnels. The Cascade Tunnel is a good example. Also see the proposed North–South Rail Link.
The electric locomotive has many advantages in mountainous terrain, including better adhesion, greater power at low speeds, no requirements for fueling or watering, and regenerative braking. The planned California High-Speed Rail system, for example requires electrification to achieve acceptable speeds through the Tehachapi Mountains.
Extremely high-traffic lines can readily recoup the high capital investment of electrification by the savings accrued during operation. The savings typically result from improved utilization of trains, and lower maintenance costs.
Short-distance commuter operations
Suburban commuter trains are an ideal subject for electrification since electric multiple units possess rapid acceleration, fast braking (sometimes regenerative braking) and the ability to change direction without running a locomotive around. It also reduces diesel locomotive emissions in relatively high-density areas.
Heavy freight trains are ideally suited to electric traction due to the greater pulling power of an electric locomotive.
Overview of electrification in the U.S.
By 1973 it was down to 1,778 route miles (2,861 km) (Class I railroads) with the top 3 being: Penn Central 829 miles (1,334 km), Milwaukee Road 658 miles (1,059 km), Long Island Rail Road 121 miles (195 km).
In 2014 the only electrified lines hauling freight by electricity were three short line coal haulers (mine to power plant) and one switching railroad in Iowa. The total electrified route length of these four railroads is 122 miles (196 km). While some freight trains run on parts of the electrified Northeast Corridor and on part of the adjacent Keystone Corridor, these freight trains use diesel locomotives for traction. The total electrified route length of these two corridors is 559 miles (900 km).
History of electrification projects in the United States
Cleveland Union Terminals Co.
In June 1929 this railroad switched from steam to electric operation on a 17-mile (27 km) route between Collinwood and Linndale in Ohio. A 3000 V DC overhead system was used. This change of operation was for smoke abatement. Electric operation ceased in 1953.
New York Central Railroad (Hudson and Harlem Divisions)
The New York Central electrified a section of its main line Hudson Division route in 1913 from New York City (Grand Central Terminal) to Harmon (now Croton-Harmon), where it changed to at first steam, then diesel power. The Harlem Division in Westchester County, New York was also electrified to North White Plains. Metro-North Railroad, the successor to New York Central's commuter operations, continues to use these lines, and extended the Harlem Line electrification to Southeast in 1984. The lines are electrified at 750 V DC with under-running third rail.
The Hudson Line is used by Amtrak for intercity passenger service to and via Albany, but these trains run to Penn Station via the Empire Connector, and only in the underground area in and near that station do Amtrak's dual-mode (diesel and electric) locomotives shift to using the overrunning DC third rail.
Baltimore and Ohio Railroad
The construction of the Howard Street tunnel through Baltimore in order to make a rail connection to New York City brought about the world's first mainline electrification. Operation began in 1895 with three General Electric locomotives. These locomotives only worked pulling northbound trains; southbound traffic simply coasted through this section, which was all downhill. Initially the system used a unique overhead track in which the current shoe rode, but shortly after it was converted to a conventional 675 V DC third rail system. The electrification was discontinued in 1952 when dieselization made it unnecessary.
Boston & Maine Railroad (Hoosac Tunnel)
The Hoosac Tunnel was electrified by the Boston & Maine Railroad in May 1911. This was done to speed up trains and to reduce smoke in the tunnel. Electricity was provided from the Zylonite power plant in Adams, MA. The electrification was switched off in August 1946 with the arrival of diesel locomotives on the route.
Grand Trunk Railway (St. Clair Tunnel)
The St. Clair Tunnel is the name for two separate rail tunnels which were built under the St. Clair River between Sarnia, Ontario and Port Huron, Michigan. It was the first full-size (i.e. able to allow a railroad to run through it) subaqueous tunnel built in North America.
Steam locomotives were used in the early years to pull trains through the tunnel, however concerns about the potential dangers of suffocation should a train stall in the tunnel led to the installation of catenary wires for electric-powered locomotives by 1907. The first use of electric locomotives through the tunnel in regular service occurred on May 17, 1908.
The electric-powered locomotives were retired in 1958 and scrapped in 1959 after CNR retired and scrapped its last steam-powered locomotives on trains passing through the tunnel. New diesel-powered locomotives did not cause the same problems with air quality in this relatively short tunnel.
Great Northern Railway (Cascade Tunnel)
The Great Northern Railway (now BNSF Railway) electrified the 2.5-mile (4.0 km) original Cascade Tunnel in 1909, near the summit of Stevens Pass in the Cascade Mountains. This first electrification system with GE-built boxcabs were the only three-phase AC power ever used on North America railroads, see Three-phase AC railway electrification. The electric boxcabs pulled trains through the tunnel with their steam locomotives still attached until they were retired in 1927.
In 1925 work began on the new 7.8-mile (12.6 km) Cascade Tunnel, with the Great Northern ultimately electrifying a 73-mile (117 km) section of its main line route to Seattle, Washington from Wenatchee to Skykomish. The new tunnel and electrification reduced the mainline by 9 miles (14 km), eliminated 502 feet (153 m) of elevation and 6 miles (9.7 km) of snow sheds. Electric locomotives handled mainline freight and passenger trains on this section exclusively. The route was de-energized and catenary dismantled in 1956, after the Cascade Tunnel was fitted with ventilation fans.
Hudson & Manhattan Railroad (Hudson River Tubes)
The Hudson & Manhattan Railroad, a rapid transit system, was built between New York, Hoboken and Jersey City, opening in 1908. The system operates through two tunnels beneath the Hudson River; the Uptown Hudson Tubes that go from New Jersey to Greenwich Village, and the Downtown Hudson Tubes that go to the World Trade Center. It was designed as an electrified system using 600 V DC third rail. The system was taken over by Port Authority Trans-Hudson in 1962, and still operates today.
Butte, Anaconda and Pacific Railway
The Butte, Anaconda and Pacific Railway (BA&P), a copper ore-hauling short line in Montana, electrified in 1913 using a 2,400 V DC system engineered by General Electric. It was the first primarily freight railroad in North America to electrify. Original motive power was in the form of 28 identical B-B boxcabs, which served until de-electrification in 1967, by which time diesel-electric locomotives were cheaper to run. GE used the BA&P as a model railroad for demonstrating the success of its DC electrification techniques. The Milwaukee Road electrified soon afterward using a similar technique at 3,000 V DC.
Chicago, Milwaukee and St. Paul Railroad (the Milwaukee Road)
The Chicago, Milwaukee and St. Paul Railroad ('Pacific' was not added to the title until incorporation in 1927) electrified two of its mountainous divisions using a DC overhead system. The two divisions were widely separated from each other, but plans to electrify the intervening 212 miles (341 km), the relatively flat Idaho Division from Avery to Othello, were never implemented.
The electrification system was similar to that of the Butte, Anaconda & Pacific, but was at 3000 V DC rather than 2400 V DC. The higher voltage was chosen because of the load conditions with 2,500 ton trains.
Rocky Mountain Division (Harlowton to Avery)
The first division to be electrified was the Rocky Mountain Division from Harlowton, Montana to Avery, Idaho. This covered a distance of 438 miles (705 km) and began electric operation in 1917. The electrification remained in operation until 1974, when diesel locomotives took over. There were two main reasons for electrifying this division. The first was to get through the Bitter Root Mountains, which are steeply graded. The second was that the line passes through an important forest reserve of the US Government. Steam trains were a fire hazard, and thus electric trains lessened the risk.
Coast Division (Othello to Tacoma/Seattle)
The second division to be electrified was the Coast Division between Othello, Washington to Tacoma, and to Black River just south of Seattle. This covered a distance of 207 miles (333 km) and began electric operation in 1919. The electrification remained in operation until 1972, when diesel locomotives took over. The main reason for electrifying was to get over the Saddle Mountains.
Norfolk and Western Railway
The Norfolk and Western Railway (N&W) had an electrified district of 52 miles (84 km) from Bluefield to Iaeger, West Virginia, between 1913 and 1950. It was an 11 kV, 25 Hz overhead electrification in a mountain region with a major tunnel (Elkhorn Tunnel).
The VGN had an electrified district of 134 miles (216 km) of mountainous terrain built in the 1920s from Roanoke, Virginia to Mullens, West Virginia. It went to the N&W with the 1959 merger and was de-electrified in 1962.
Amtrak, the national intercity passenger railroad, inherited a 1930s-era 11 kV 25 Hz electrification system from the Pennsylvania Railroad (PRR), which it is slowly modernizing, and has completed two electrification projects on its own lines.
A short portion of the Empire Connection was electrified when it was built in 1991, allowing trains from Albany direct access to Penn Station New York by use of dual-mode locomotives. Track near the terminal was electrified with 750 V DC third rail, compatible with the third rail system used within Penn Station by the Long Island Rail Road (LIRR).
The Northeast Corridor mainline from New Haven to Boston was electrified in 1999, completing the thwarted ambition of the former New York, New Haven and Hartford Railroad. This electrification was part of the Acela Express high-speed project, and involved the building of overhead lines electrified at 25 kV 60 Hz, requiring trains to handle a change of voltage on the fly at New Haven. Plans to convert the rest of the Northeast Corridor to 60 Hz have been shelved, although the section from New Haven to the Hell Gate Bridge has been converted to 60 Hz by Metro-North.
Boston, Revere Beach and Lynn Railroad
This railroad changed from steam to electric operation in 1928 using a 600 V DC overhead system. The company filed for bankruptcy in 1937, and ceased operating in 1940. In 1952 a section of the line between East Boston and Revere was bought by the MBTA and is now a part of the Blue Line. The remainder of the line to Lynn is owned by the Commonwealth of Massachusetts and may be used for further expansion of the Blue Line.
Erie Railroad (Rochester Division)
In June 1907, the Erie Railroad changed from steam to electric operation on its Rochester Division. A single phase AC system was used operating at 11 kV 25 Hz. The electrified section was between Rochester, NY to Mount Morris, NY, a distance of 34 miles (55 km). The system lasted in operation until 1934.
New York, New Haven and Hartford Railroad
The New York, New Haven and Hartford Railroad completed electrification in 1907 of its New Haven–New York City mainline and was one of the pioneers of heavy electric railway use in the United States. The New Haven chose the 11 kV 25 Hz system, later used by the PRR, in addition to working with Westinghouse to develop AC/DC electric motors (locomotives) to run on both AC overhead lines and DC third rail. The main line, now Metro-North Railroad's New Haven Line, was converted to 12.5 kV 60 Hz in 1985.
The Pennsylvania Railroad carried out many electrification projects.
West Jersey and Seashore Railroad
The PRR, owner of West Jersey & Seashore Railroad (WJ&S), electrified with 600 V DC from Camden, New Jersey to Atlantic City, via Newfield, and to Millville. A third-rail system was used for most of the line except overhead trolley wire was installed between Mickle Street in Camden and Gloucester City as well as a 10-mile (16 km) segment between Newfield and Millville. The Camden-Gloucester City portion was installed due to a decision to use the old Camden Seventh Street line as part of the route. Numerous grade crossings on both this segment and in Gloucester City precluded the use of third rail due to public safety considerations. The Millville branch, however, was equipped with overhead wire as a "method of comparing the durability of trolley wire versus third rail under high-speed open-country operating conditions." The WJ&S ordered 62 coaches and six combination baggage mail units split between Jackson and Sharp Company, and J. G. Brill and Company at Philadelphia, which had 46 cars from the order. Brill sublet work on 22 coaches to its Wason subsidiary in Springfield, Massachusetts.
The electrification was opened in 1906 with cars that resembled wooden interurbans of other electric traction properties. The same year the 1906 Atlantic City train wreck occurred, in which a three-car train of the new equipment derailed and fell into a waterway; 53 people died. Other cars were built in 1909 bringing the fleet total to 80 MP1 and MP2 class wooden MU coaches. The 19 purchased in 1909 had steel instead of wooden ends and featured PRR porthole style windows on each end. There were six MO1 class passenger-baggage combines including two with steel ends, four MBM1 baggage-mail cars and two MB1 baggage-express cars. In 1912, the PRR assigned two MPB54 all-steel combines and 15 all-steel MP54 coaches to WJ&S. WJ&S and the Reading subsidiary Atlantic City Railroad were merged into Pennsylvania-Reading Seashore Lines (P-RSL) in 1932.
Electric MU service between Newfield and Atlantic City ended Sept. 26, 1931 so P-RSL only inherited the electrified Millville commuter rail service from WJ&S. On Oct. 20, 1948, New Jersey's public utility regulators ordered P-RSL to remove all remaining 26 wooden MU coaches from service as a safety hazard should they be involved in fire or collision. P-RSL management already was considering replacing the MUs due to an aging power distribution system and obsolete rolling stock. So nearly two-thirds of the MU fleet was removed from service. With only the PRR style all-steel MUs left for passenger service, P-RSL cut back the electrified commuter service to Glassboro in fall 1948 and management then ordered an end to all remaining electrification as of Sept. 8, 1949. On that date a morning commuter run from Glassboro to Camden ended 43 years of electrification. Non-electrified commuter rail service to Glassboro and Millville continued until March 5, 1971.
New York Terminal
Electrification was installed from Sunnyside Yard in Queens, through New York station to Manhattan Transfer station in New Jersey. A 675 V DC third rail (Top Contact) system was used. Electrification was later changed to 11 kV 25 Hz overhead catenary, when the PRR electrified its mainline to Washington, D. C. in the early 1930s. Third rail is still installed in the East River Tunnels in order to provide power the LIRR trains. Third rail is also installed in the North River Tunnels for use in emergencies should power be lost to the overhead catenary.
A section of the Chicago-Philadelphia Main Line (now part of Amtrak's Keystone Corridor) was electrified in 1915. The suburban service between the former Broad Street Station in Philadelphia and the village of Paoli. The PRR electrification utilized overhead catenary wires electrified at 11 kV 25 Hz, and was fed by two substations, one in Philadelphia and another in Ardmore. It was expanded in 1919 on the PRR's Chestnut Hill line, and in the 1920s on the Philadelphia-Washington, D.C. main line between Philadelphia and Wilmington, and on the West Chester Line between Philadelphia and West Chester, with the latter two lines being fed through a single substation located in Chester.
New York - Washington
Extensive electrification after 1925 occurred on the PRR's New York-Washington line (now part of the Northeast Corridor), the Chicago-Philadelphia Main Line between Paoli and Harrisburg, several major commuter lines in Pennsylvania and New Jersey, and on major low-grade, through-freight lines, including the Trenton Cutoff, the Atglen & Susquehanna, Port Road, Philadelphia & Thorndale, Shellpot, and Enola branches. All electrification done after 1919 used the same catenary supports used on the Paoli commuter line, but with the catenary being supplied with 100 kV 25 Hz "transmission" lines with the voltage stepped-down at substations located every 10 to 20 miles (16 to 32 km). The PPL-owned Safe Harbor Dam, located near the Exelon-owned Peach Bottom Nuclear Power Plant between Conowingo, Maryland and York, Pennsylvania, supplies the power for all post-1925 electrical expansion projects, while Exelon supplies the pre-1925 electrification areas through the existing Philadelphia, Ardmore, and Chester substations. Plans were made in the thirties to extend electrification to Pittsburgh, but were not pursued due to the Great Depression.
Since its takeover by Amtrak in 1976, both the Northeast and Keystone Corridors are undergoing extensive wire replacements, either by Amtrak or SEPTA, while the through-freight branches taken over by Conrail have been de-electrified and freight operations carried out by diesel locomotives. Those lines that were de-electrified, but have transmission lines are maintained by Amtrak through arrangements through Conrail's successors, Norfolk Southern and CSX Transportation.
Rock Island & Southern Railway
This railroad electrified 52 miles (84 km) between Rock Island and Monmouth, Illinois using a 11 kV 25 HZ system.
Spokane & Inland Empire Railroad
In 1906, this railroad electrified from Spokane to Colfax, Washington and Moscow, Idaho using a 6600 V 25 Hz system.
Suburban Commuter Operations
Delaware, Lackawanna and Western Railroad / Morris and Essex Railroad
What are now New Jersey Transit's Morris & Essex Lines (the Morristown Line and Gladstone Branch) and Montclair-Boonton Line were electrified by the Delaware, Lackawanna and Western Railroad at 3000 V DC in 1930/31. By August 1984 the lines had all been converted to 25 kV 60 Hz by NJ Transit.
Electrification on the Reading Railroad began during the late 1920s. The first stage was placed in operation on July 26, 1931, when electric suburban trains began serving the Bethlehem Branch between Reading Terminal, Philadelphia and Lansdale, the Doylestown Branch between Lansdale and Doylestown, the New Hope Branch between Glenside and Hatboro, and the Jersey City Branch between Jenkintown and West Trenton, New Jersey. The second stage, the Norristown and Chestnut Hill branches, was opened on February 5, 1933. Like the PRR Paoli commuter line, the Reading employed overhead catenary wire powered at 11 kV 25 Hz, but unlike the PRR, the Reading used a single generator, located at Wayne Junction, with long-distance lines being supplied by spider-frame pylons that can still be seen, mostly along the Schuylkill Expressway (I-76).
Extensions of electrification over intercity lines, such as West Trenton-Jersey City, Norristown-Reading-Harrisburg, and Lansdale-Bethlehem were planned, but because of the Great Depression, they were dropped. Only two expansion projects, carried out by the Reading with funding from SEPTA, were that of the Newtown Branch between Newtown Junction and Fox Chase in September 1966, and the Warminster Branch between Hatboro and Warminster in 1974.
Since the takeover of the Reading commuter lines in 1983, SEPTA has rehabilitated the catenary wires between the Center City Commuter Connection and Wayne Junction, and on all ex-Reading tracks owned by SEPTA. Those sections of ex-Reading tracks owned by Conrail, and later by CSX, are being done on a step-by-step basis.
Illinois Central Railroad
The Illinois Central Railroad electrified its three commuter lines serving Chicago in 1926 pursuant to ordinances passed by the city. The IC commuter lines remain electrified and are now operated as Metra Electric. The catenary is energized at 1500 V DC and serves four tracks of commuter operations. Two tracks are unelectrified and used for freight and Amtrak service to downstate Illinois and beyond.
Long Island Rail Road
The Long Island Rail Road's electrification was initiated in the first decade of the 20th century while it was owned by the Pennsylvania Railroad, which was building tunnels under the Hudson River and East River to gain access to Manhattan. The first segment of the LIRR to be electrified was the trackage between the Atlantic Avenue terminal in Brooklyn and Jamaica station. Electrification extended east of Jamaica to the Belmont Park station in 1905. In 1910, the opening of Pennsylvania Station (New York City) ushered in electric service between that station and Jamaica. The LIRR's Port Washington Branch was rebuilt and electrified by 1918. By 1934, LIRR branches to Mineola, Hempstead, West Hempstead, Far Rockaway, Long Beach, and Babylon were electrified. In 1970, electrification was extended to Hicksville, and to Huntington on the Port Jefferson Branch. In 1987, electrification of the Main Line between Hicksville and Ronkonkoma was completed, resulting in greatly increased service.
The LIRR utilizes third rail electrification, which was the original method used by the PRR. By the 1930s, the PRR had switched to overhead catenary electrification, but the LIRR has continued utilizing its third rail system. Voltage was increased from 600 V DC to 750 V DC in the early 1970s to meet the greater power needs of the railroad's new M-1 cars.
New York, Westchester and Boston Railway
This railroad converted the operation of its suburban train service from steam to electric. The 4-track main line ran for 7 miles (11 km) from Westchester Ave. in New York to Mount Vernon, NY. From Mount Vernon the line split into two 2-track lines; one to New Rochelle, NY (2 miles (3.2 km)) and a second to White Plains, NY (9.4 miles (15.1 km)).
The Caltrain Modernization Program (CalMod) is a $1.9 billion project that will electrify the railroad's main line, which serves cities in the San Francisco Peninsula and Silicon Valley. Caltrain service has existed in its current form since operated as the Peninsula Commute by Southern Pacific, but proposals for electrifying the line began as early as 1992. The project lay dormant due to lack of funding until Caltrain agreed to share its tracks with the California High-Speed Rail Authority. CalMod will electrify 51 miles (82 km) of tracks between 4th and King station and Tamien Station and plans to be completed the project by 2021. New electrical infrastructure includes installation of approximately 130 to 140 miles (210 to 230 km) of 25 kV 60 Hz single-phase AC overhead contact lines and ten new power stations (two traction power stations, a switching station approximately halfway along the line, and seven paralleling stations).
Texas Transportation Company
Main article: Texas Transportation Company
The Texas transportation Company Operated a Small Class III railroad in San Antonio until 2001, mostly serving the Pearl Brewery. It had a connection to the Southern Pacific Railroad, and briefly hosted passenger service in the 1980's with a former San Antonio trolly.
Black Mesa and Lake Powell Railroad
The BM&LP is an isolated short line in Arizona which hauls coal from a mine near Kayenta to the Navajo Generating Station power plant at Page. When built in 1973, it was the first line to use 50 kV 60 Hz overhead catenary. The coal it hauls on the 78 miles (126 km) is used by the power plant at its western terminus to power the line itself. The line does not connect to any other part of the American freight rail network.
Muskingum Electric Railroad
This line operated between a coal mine and power generation station in southeast Ohio. It was electrified its entire life from its construction in 1968 to its dismantling around 2004. The line utilized 50,000 volt AC catenary to power GE E40C locomotives.
Mason City & Clear Lake Traction Co.
This is a 10-mile line in Iowa that was built to connect Mason City with Clear Lake. Initially it operated a passenger service using a 600 V overhead system. In 1961 it was sold to investors and renamed as Iowa Terminal. In 1987 the line was purchased once more and was renamed to Iowa Traction Railway (IATR) where it now operates as a freight only railway.
- Middleton, William D. (1974). When the Steam Railroads Electrified. Kalmbach Publishing Co. ISBN 0890240280.
- Wadsworth, G.R. (October 20, 1905). "Terminal Improvements of the New York Central & Hudson River in New York". Railroad Gazette. 39: 366.
- "Report of Chicago Committee on Smoke Abatement and Terminal Electrification". Electric Railway Journal. XLVI (23). Dec 1915.
- "2012 Business Plan" (PDF). www.cahighspeedrail.ca.gov. California High-Speed Rail Authority. pp. 2–17. Archived from the original (PDF) on 2012-11-12.
It is important to note that high-speed, electrified train service is the only effective means to close this Bakersfield-to-Palmdale passenger rail gap. ... Electrified trains can efficiently ascend greater gradients and maintain higher speeds climbing and descending the Tehachapi Mountains. Thus, the only effective means to bring intercity passenger rail service across the mountains that separate Los Angeles from the Central Valley is with an electrified high-speed rail line...
- Morgan, David P. (July 1970). "The Mystique of Electrification". Kalmbach Publishing: 44–47.
- Morgan states that electrification reached its peak (in the U.S.) of 3100 miles (1.23% of route-miles) but fails to give a date. But from the context, the date is between 1924–1957. The last major electrification was by the Pennsy (Pennsylvania Railroad) during the Great Depression of the 1930s, so one may guess that since electrified mileage had decreased by 2⁄3 by 1957 (per Morgan) that the peak was well prior to 1957. With the big Pennsy electrification going on in the 1930s, total electrified mileage was perhaps increasing. This reasoning puts the peak at the end of the 1930s.
- Дмитриев, B.A. (1976). "Народнохозяйственная эффективность электрификации железных дорог и примениния тепловозной тяги" [National economic effectiveness of railway electrification and application of diesel traction]. Транспорт (Transport) (in Russian). Москва(Moscow): 116. Dmitriev claims that there was almost no new electrification in the US from 1938-1973 which lends more credibility to the guesstimated time of the peak.
- "Transport statistics in the United States, Part I: Railroads, Second Release, Roadway and Track". Washington D.C.: Interstate Commerce Commission (Bureau of Accounts).
Data on the extent of US electrification was available in a table in this annual US government publication which gave the data for one year only. Each publication listed electrified mileage operated by kind of track, by district, and by railroad, Class I line-haul railroads.
- "Electric freight railroads in the US".
- "Cleveland Terminal Electrification Plans Completed". Electric Railway Journal. 73 (17). August 1928.
- American Railroad Association (1922), p. 900.
- Harwood Jr., Herbert H. (1990). Royal Blue Line. Sykesville, Md.: Greenberg Publishing. ISBN 0-89778-155-4.
- "Electrification of the Hoosac Tunnel". Electric Railway Journal. 38 (1). July 1911.
- American Railroad Association (1922), p. 901.
- Howes, Mark. "Hoosac Tunnel History". www.HoosacTunnel.net.
- "Progress on the C.M. & St. P. Electrification". Electric Railway Journal. XLVI (16). 1915-10-16.
- Manson, Arthur J. (1923). Railroad Electrification and the Electric Locomotive. New York, NY: Simmons-Boardman Publishing Corporation. ISBN 978-587167932-6.
- "The Electrification of the Norfolk & Western Railway". Electric Railway Journal. June 1915.
- Doyle, Lee P. (January 1926), The Virginia Railway Electrification, Vol. 9, No. 2, The Ohio State Engineer, pp. 11–13 and 38, retrieved 2011-03-01
- Austin, Edwin (1915). Single-Phase Electric Railways. New York: D. Van Nostrand.
- Moreland, Edward L. (June 1931). "Lackawanna Suburban Electrification". Transactions of the A.I.E.E.: 618–631.
- "The Gladstone Branch". Long Hill Township, Morris County, NJ (Unofficial website). Archived from the original on January 13, 2011. Retrieved August 12, 2015.
- Middleton, William D. (March 2002). When the Steam Railroads Electrified (2nd ed.). Bloomington, Indiana: Indiana University Press. ISBN 978-0-253-33979-9.
- Huneke, Arthur John. "Arrt's Archives". Arrt's Archives. Retrieved 2012-09-18.
- Caltrain 2015, Figure 2-2, Chapter 2: Project Description