Old Main Line Subdivision

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Ellicott City Station, built 1830, is the oldest surviving passenger station in the United States. Photo taken in 1970, looking south towards Baltimore.
Old Main Line
Baltimore Terminal Subdivision
0.0 RelayWashington Branch
2.5 Orange Grove
3.2 Ilchester Tunnel
3.5 Ilchester Bridge
3.6 Ilchester
4.4 Lees
4.7 Gray
5.7 Ellicott City
6.2 Sucker Run Bridge
7.9 Union Dam Tunnel
9.2 HS Tower
9.5 Hollofield
10.6 Daniels Bridge
10.9 Alberton
11.6 Brice Run Bridge
12.1 Dorsey’s Run Tunnel
12.7 Eureka Bridge
12.8 Line Run Bridge
12.9 Davis Tunnel
13.3 Davis
13.8 Davis Branch Bridge
14.6 Woodstock
17.1 Marriottsville
17.7 Henryton Bridge
17.8 Henryton Tunnel
17.9 Henryton
19.7 Gorsuch
21.6 Sykesville
22.4 Sykesville Tunnel
22.9 Gaither
24.2 Hood’s Mill
26.1 Morgan
26.5 Woodbine Tunnel
26.8 Woodbine
26.9 Gillis Falls Bridge
29.5 Watersville
30.6 Watersville Junction
31.8 Mount Airy
32.6 Mount Airy Tunnel
33.9 Mount Airy Junction
37.4 Bush Creek Bridge
39.5 Monrovia
40.0 Monrovia Tower
42.9 Ijamsville
44.1 Hartman Tunnel
46.1 Reel’s Mill
47.4 Monocacy River Bridge
47.5 Frederick JunctionFrederick Branch
43.5 Frederick(South Market Street)
48.9 Ballenger Creek Bridge
50.0 Lime Kiln
51.7 Buckeystown
53.7 Adamstown
53.9 Adamstown Junction
Adamstown Cutoff
58.0 Washington Junction(Point of Rocks)
Metropolitan Branch
58.5 Point of Rocks Tunnel
60.1 Catoctin Tunnel
to Brunswick

The Old Main Line Subdivision is a railroad line owned and operated by CSX Transportation in the U.S. state of Maryland. The line runs from Relay (outside Baltimore) west to Point of Rocks, and was once the main line of the Baltimore and Ohio Railroad, one of the oldest rail lines in the United States. At its east end, it has junctions with the Capital Subdivision and the Baltimore Terminal Subdivision; its west end has a junction with the Metropolitan Subdivision.


The initial route of the Baltimore and Ohio Railroad (B&O) followed the Patapsco River valley west out of Baltimore, with the first section (to what is now Ellicott City, Maryland) opening for service in 1830.[1]:21 The line left the valley to cross Parr's Ridge, which, after an abortive attempt to use a system of inclined planes, was crossed via a more round-about routing through Mount Airy. It continued west to Harper's Ferry, West Virginia, passing south of Frederick on the way. This line was the only route west out of Baltimore until the Metropolitan Branch was constructed from Washington, DC to Point of Rocks in the 1870s. The section of the original route from Relay (where the Washington Branch began) to Point of Rocks became known as the "Old Main Line" (or "OML" for short) as it was relegated to secondary status, and continues to be known as the Old Main Line Subdivision in CSX timetables.

Initial improvements[edit]

Since railroad technology was in its infancy, the engineers of the B&O made many design decisions which quickly proved to be mistaken. The route was laid out to minimize grades at the expense of curvature; elimination of the resulting sharp curves led to the construction of many tunnels over the next century. The planes over Parr's Ridge arose from the same decision, and they gained the distinction of becoming one of the first railroad main line right-of-way abandonments in history.

Initially a system of granite stringers and strap rail was preferred, although time, expense, and difficulty in obtaining sufficient granite led to the substitution of wooden ties and heavier "T-rails" for much of the route, beginning in the 1840s.[1]:39 In the 1850s, when Benjamin Henry Latrobe, II was chief operating engineer, the need to address these deficiencies became acute, and a variety of improvements were made, subject to the railroad's limited resources at the time. All of the granite stringers and strap rail were replaced, and certain realignments were made. Among these was the "Elysville cutoff," where a pair of bridges were constructed to bypass a sharp curve on the south side of the river. In making these improvements, older structures were simply abandoned. The granite stringers of the original roadbed were simply left in place and buried.

B&O built its first tunnel in 1850 at Henryton. The Henryton Tunnel was widened for double track in 1865, after the Civil War.[1]:47, 452

The flood of 1868[edit]

In 1868 a freak storm flooded the Patapsco and severely damaged the railroad, as well as washing away many of its customers. Most of the railroad was rebuilt, but with many alterations to the surviving structures. For instance, all but one arch of the Patterson Viaduct at Ilchester were washed away; the railroad retained the remaining arch to use as an abutment for the Bollman truss bridge which replaced the viaduct.

Station building[edit]

The first station on the line was built in Ellicott City in 1830, Over the years this station was modified and enlarged, and it survives to this day. The next station erected was a freight depot in Frederick, built 1831. Another simple station was built in Mt. Airy, which also survives.

In the 1870s and 1880s, the railroad undertook a program of station building. Most of these were designed by E. Francis Baldwin and several towns on the Old Main Line received such stations, erected in either wood or brick. The most famous of these, at Point of Rocks, still stands in the wye between the OML and the Metropolitan Subdivision. Other stations were built at Sykesville, Ilchester, and Woodstock, though not all survive.

Improvements under Leonor F. Loree[edit]

In 1901 Leonor F. Loree was installed as president of the railroad. Among other projects, he initiated a reassessment of the Old Main Line which led to a project of systematic improvements. Much of the original route and many reroutings were abandoned in favor of new routes along the valley. Many new tunnels were cut, and new bridges were built along new alignments. In particular the Mt. Airy Cutoff tunnelled through Parr's Ridge and reduced the old line through Mt. Airy to a spur. (Ironically the west end of the spur met the main line at the base of Plane 3, the middle of the western half of the original inclined plane system.) B&O maintained the spur as a loop until 1957, when the eastern end was abandoned.[1]:174 [2]

At the west end of the line, the Adamstown Cutoff was built to allow operation of coal drags over the OML, minimizing the use of helpers. A water and coaling stop was added at Reels Mill to support this. In practice the operation was not successful, and the cutoff was discontinued, though it was not pulled up for decades.

Decline and Agnes[edit]

Following the opening of the Metropolitan Branch in 1873, the B&O routed its through passenger trains via Washington, and passenger service on the OML became strictly local. By 1928, only three passenger trains left Baltimore on the OML each day.[1]:160–162 The area lacked industry, and the granite mines at the east end of the valley did not last. Therefore, service declined steadily. During World War II, however, traffic rose dramatically, and a new water and coal station was added at Gaither to allow engines to be serviced outside the congestion of Baltimore City. The facilities were closed shortly after the end of the war, and all passenger service ended soon after. In 1959 the line was reduced to single track to increase the clearance through the tunnels, and Centralized Traffic Control (CTC) was introduced.[1]:174

In 1972 Hurricane Agnes flooded the valley again, washing out large portions of the line. The B&O considered abandoning the line, and several years passed before service was restored. For many years much of the line remained dark (i.e. operating without signals), but eventually the entire line was re-signalled.

MARC service[edit]

The MARC commuter rail system originally did not serve any portion of the OML, though there was always service over the oldest portion of the line into Baltimore and from Point of Rocks to Washington. In the late 1990s, however, commuter traffic to Washington from Frederick had grown substantially, and MARC service between the two cities was initiated. The existing wye which connected the two lines at Point of Rocks station was upgraded to take through traffic, and trains were thus able to follow the OML up to Frederick Junction and then into town. This service remains the only scheduled passenger operation over the OML.


After the initial push, the builders of the OML tended to prefer very permanent materials—stone and iron—over the wooden structures used elsewhere. And since much of the river valley became part of the Patapsco Valley State Park, the area along the line contains an uncommonly large range of early 19th century railroad artifacts and structures, readily accessible to the railfan. In many places even the granite stringers of the original roadbed can be seen.

Some of the more notable relics are:

See also[edit]


  1. ^ a b c d e f Harwood, Jr., Herbert H. (1979). Impossible Challenge: The Baltimore & Ohio Railroad in Maryland. Baltimore, MD: Barnard, Roberts. ISBN 0-934118-17-5. 
  2. ^ Steve Okonski. "B&O Old Main Line Photo Tour – Mt. Airy Loop – East." Accessed 2009-11-06.

External links[edit]