Map of Pennsylvania with I-99 highlighted in red
|Maintained by PennDOT|
|Length:||85.6 mi (137.8 km)|
|Existed:||November 6, 1998 – present|
|South end:||I-70 / I-76 / Penna. Tpk. / US 220 near Bedford|
| PA 56 near Cessna
US 22 near Altoona
PA 453 in Tyrone
PA 350 near Bald Eagle
US 322 near State College
PA 26 near Pleasant Gap
|North end:||I-80 / US 220 near Bellefonte|
Interstate 99 (I-99) is an intrastate Interstate Highway located in central Pennsylvania in the United States. The southern terminus of the route is at exit 146 of the Pennsylvania Turnpike (I-70 and I-76) north of Bedford, where the road continues south as U.S. Route 220 (US 220). The northern terminus is at I-80 near Bellefonte. I-99 passes through Altoona and State College–the latter home to Pennsylvania State University–and is entirely concurrent to US 220. Long-term plans call for I-99 to be extended southward along the US 220 corridor to an interchange with I-68 in Cumberland, Maryland, and northward along the US 220 and US 15 corridors to an interchange with I-86 west of Corning, New York.
Unlike most Interstate Highway numbers, which were assigned by the American Association of State Highway and Transportation Officials (AASHTO) to fit into a grid, I-99's number was written into Section 332 of the National Highway Designation Act of 1995 by Bud Shuster, then-chair of the U.S. House Committee on Transportation and Infrastructure, the bill's sponsor, and the representative of the district through which the highway runs. I-99 violates the AASHTO numbering convention associated with Interstate Highways, since it lies east of I-79 but west of I-81.
Route description 
I-99 begins at an indirect interchange with US 220 and the Pennsylvania Turnpike (designated as I-70 and I-76) north of Bedford. It begins concurrent with US 220, which continues south from the interchange toward the Maryland state line as a two-lane highway known as the Appalachian Thruway. The interchange with the Turnpike requires drivers to use a short segment of US 220 Business to access the Turnpike at exit 146. North of the Turnpike junction, the limited-access highway becomes the Bud Shuster Highway as it heads through a rural portion of Bedford County. It connects to Pennsylvania Route 56 (PA 56) just west of the Bedford County Airport at exit 3 and PA 869 at exit 7 before crossing into Blair County. Here, it meets PA 164 north of East Freedom at exit 23 prior to entering the Altoona area.
In Hollidaysburg, a borough south of the city, I-99 and US 220 connect to US 22 at exit 28, a large modified trumpet interchange. This junction allows travelers to head west towards Ebensburg, Johnstown, and Pittsburgh. The freeway continues to Altoona itself, where it indirectly connects to PA 36 via exit 32. Unlike the original routing of US 220 which goes through the city center, I-99 and US 220 mostly bypass it to the east, connecting to the city via streets leading eastward from the downtown district. At the northern edge of Altoona, PA 764 joins the old alignment of US 220 and parallels I-99 north for 3 miles (5 km) toward Bellwood. PA 764 leaves old US 220 about 2 miles (3.2 km) south of Bellwood, however, and terminates at I-99 exit 39. Bellwood itself is served by exit 41, which leads to PA 865.
The highway veers northeastward from Bellwood to serve the borough of Tyrone, located at the junction of old US 220 and PA 453. Access to the borough is made by way of exit 48, which serves PA 453. Past Tyrone, I-99 and US 220 head through sparsely populated areas of Blair and Centre Counties. For this reason, only three exits exist between Tyrone and State College: exit 52, serving PA 350 and the small community of Bald Eagle, and exits 61 and 62, which connect to US 322 and the borough of Port Matilda. Here, US 322 joins I-99 and US 220 and follows them eastward to the State College area.
At exit 68 (US 322 Business), I-99 merges into the Mount Nittany Expressway, an older, northerly bypass of State College. I-99, US 220, and US 322 follow the expressway to the Mount Nittany Interchange, a directional T interchange located on the northern fringe of the Pennsylvania State University campus. US 322 continues east through the interchange to follow the Mount Nittany Expressway while I-99 and US 220 split from US 322 and head northeastward toward Pleasant Gap, which I-99 connects to via exit 81 and PA 26. At this point, PA 26 joins the freeway and follows it to Bellefonte, served by exit 83 and PA 550. I-99 ends about 2.5 miles (4.0 km) later at an interchange with I-80, where PA 26 continues north and US 220 joins I-80 east.
Corridor O of the Appalachian Development Highway System was assigned in 1925, running from Cumberland, Maryland (Corridor E, now I-68) to Bellefonte (I-80) along US 220. The portion in Pennsylvania, from Bedford north to Bald Eagle, was upgraded to a freeway in stages from the 1960s to the 1990s. The first section, from US 30 in Bedford to PA 56 near Cessna, opened in the latter half of the 1960s. Two more sections—from PA 56 north to modern exit 15 in Blair County and from Charlottsville (exit 45) to Bald Eagle—were completed in the 1970s. The portion between exit 15 and Altoona (exit 33) was finished in the 1980s while the segment between modern exits 33 and 45 was opened by 1997.
In 1991, the Intermodal Surface Transportation Efficiency Act (ISTEA) was signed into law. It included a number of High Priority Corridors, one of which—Corridor 9—ran along US 220 from Bedford to Williamsport, and then north on US 15 to Corning, New York. The National Highway Designation Act of 1995 amended ISTEA; among these amendments were that "the portion of the route referred to in subsection (c)(9) [Corridor 9] is designated as Interstate Route I-99." This was the first Interstate Highway number to be written into law rather than to be assigned by AASHTO. The number was specificated by Representative Bud Shuster, who said that the standard spur numbering was not "catchy"; instead, I-99 was named after a street car, No. 99, that took people from Shuster's hometown of Glassport to McKeesport. I-99 violates the AASHTO numbering convention associated with Interstate Highways, since it lies east of I-79 but west of I-81.
Designation and Bald Eagle Ridge 
On November 6, 1998, AASHTO formally approved the I-99 designation, which initially extended 51.2 miles (82.4 km) from the Pennsylvania Turnpike in Bedford to PA 350 in Bald Eagle. In 2002, plans were set in motion to extend I-99 northeast from Bald Eagle to State College via Port Matilda. The extension was fraught with issues, however. The proposed alignment for the highway north to Port Matilda proved to be controversial: while environmentalists called for I-99 to be constructed in the valley below Bald Eagle Ridge, the Pennsylvania Department of Transportation (PennDOT) and valley residents favored a routing that took the freeway above the valley and along the side of the ridge. Farther north, the widening of Skytop, the mountain cut that US 322 uses to traverse Bald Eagle Ridge, resulted in the exposure of acidic pyrite rock in 2003.
Work on the segment ceased one year later as PennDOT attempted to stop the flow of acidic runoff from the site. The state remedied the situation by removing 1,000,000 cubic yards (760,000 m3) of pyrite and replacing it with a mix of limestone and fill, a process that took two years and cost $83 million. A sediment pond is visible to the south of the road, at west of the PA 550 overpass. With the environmental issues settled, construction resumed on the portion of the freeway south of Skytop Mountain. The section from Bald Eagle to Port Matilda was opened to traffic on December 17, 2007, while the remaining section between Port Matilda and the west end of the Mount Nittany Expressway near State College was completely opened on November 17, 2008. In all, the Bald Eagle – State College section of I-99 cost $631 million to construct.
I-99 was extended northeastward to meet I-80 northeast of Bellefonte following the completion of the Bald Eagle – State College segment. The connection was made by way of the pre-existing Mount Nittany Expressway and another, unnamed limited-access highway connecting the State College bypass to the Bellefonte area. The portion of the latter highway north of the PA 26 interchange was originally built in the 1970s as a two-lane freeway connecting Pleasant Gap to I-80. At the time, it was designated solely as PA 26. It was widened to four lanes in 1997. The piece connecting the PA 26 freeway to the Mount Nittany Expressway was completed in 2002. US 220 was rerouted via US 322 and the new road, and the old alignment of US 220 north of US 322 was designated US 220 Alternate on May 30, 2003.
Long-term plans for I-99 call for the freeway to be extended northeastward along US 220 from Bellefonte to Williamsport and northward along US 15 from Williamsport to I-86 in Corning, New York. Signs have been placed along the present US 220 and US 15 between Bellefonte and Corning—much of which are built to Interstate Highway standards—marking the route as the "Future I-99 Corridor". The entirety of US 15 north of Williamsport is a limited-access highway save for a 4.5-mile (7.2 km) segment in New York between Lindley and Presho. Construction on the missing piece is underway and was expected to be completed in 2012, although it was delayed.
Exit list 
||This section contains a table that is missing mileposts for one or more junctions. Please help by|
||Bedford Township||0.00||0.00||US 220 south to US 30 – Cumberland||Continuation beyond I-70/I-76/Penna Tpk.|
|0.00||0.00||1||I-70 / I-76 / Penna. Tpk. – Pittsburgh, Harrisburg||Indirect connection via US 220 Business|
|2.93||4.72||3||PA 56 (US 220 Bus. south) – Johnstown, Cessna|
|East St. Clair Township||6.65||10.70||7||PA 869 – St. Clairsville, Osterburg||Low clearance at exit|
|King Township||10.13||16.30||10||Blue Knob State Park|
||Greenfield Township||14.92||24.01||15||Claysburg, King (US 220 Bus. north)|
|Freedom Township||22.88||36.82||23||PA 36 / PA 164 to US 22 east – Roaring Spring, Portage, Hollidaysburg|
|Allegheny Township||28.12||45.25||28||US 22 – Ebensburg, Hollidaysburg|
|Logan Township||30.60||49.25||31||Plank Road (US 220 Bus.)|
|31.88||51.31||32||To PA 36 (Frankstown Road)|
|Antis Township||38.62||62.15||39||PA 764 south – Pinecroft|
|41.30||66.47||41||PA 865 north – Bellwood|
|45.41||73.08||45||Tipton, Grazierville, DelGrosso's Amusement Park|
|Tyrone||47.89||77.07||48||PA 453 – Tyrone|
|Snyder Township||51.84||83.43||52||PA 350 (US 220 Bus. south) – Bald Eagle|
||Worth Township||61||Port Matilda (US 220 Alt. north)|
|62||US 322 west – Philipsburg||South end of US 322 overlap; southbound exit and northbound entrance; northbound exit is via exit 61|
|Patton Township||68||Gray's Woods, Waddle|
US 322 Bus. east (Atherton Street)
|Northbound exit and southbound entrance|
|69||Valley Vista Drive – Park Forest||Southbound exit and northbound entrance|
|College Township||73||US 322 east – State College, Lewistown||North end of US 322 overlap|
|74||Innovation Park, Penn State University||Northbound exit is part of exit 73|
|Benner Township||76||Shiloh Road|
|78||PA 150 – Bellefonte||Signed as 78A (south) and 78B (north)|
|Spring Township||80||Harrison Road||Northbound exit and southbound entrance|
|81||PA 26 south to PA 64 – Pleasant Gap||South end of PA 26 overlap|
|83||PA 550 – Bellefonte, Zion|
|North end of freeway|
|I-80 / US 220 north (US 220 Alt. south) – Williamsport, Dubois|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi|
See also 
- "Report of the Special Committee on U.S. Route Numbering to the Standing Committee on Highways". American Association of State Highway and Transportation Officials. November 7, 1998. Retrieved July 18, 2010.
- Google Inc. Google Maps – overview map of I-99 (Map). Cartography by Google, Inc. http://maps.google.com/maps?f=d&source=s_d&saddr=40.057583,-78.517853&daddr=I-99+N%2FPA-26+N&geocode=%3BFSy6cAIdQABe-w&hl=en&mra=mi&mrsp=0&sz=16&sll=40.057069,-78.513815&sspn=0.012055,0.027831&ie=UTF8&z=16. Retrieved July 18, 2010.
- "Status of the Appalachian Development Highway System as of September 30, 2009". Appalachian Regional Commission. December 2009. Retrieved July 18, 2010.
- Sun Oil Company (1964) (PDF). Pennsylvania (Map). Cartography by H. M. Gousha Company (1964–65 ed.).
- Pennsylvania Department of Highways (1970) (PDF). Official Map of Pennsylvania (Map). ftp://ftp.dot.state.pa.us/public/pdf/BPR_pdf_files/Maps/Statewide/Historic_OTMs/1970fr.pdf. Retrieved July 18, 2010.
- Pennsylvania Department of Transportation (1980) (PDF). Commonwealth of Pennsylvania Official Transportation Map (Map). ftp://ftp.dot.state.pa.us/public/pdf/BPR_pdf_files/Maps/Statewide/Historic_OTMs/1980fr.pdf. Retrieved July 18, 2010.
- Pennsylvania Department of Transportation (1989) (PDF). Pennsylvania Official Transportation Map (Map). ftp://ftp.dot.state.pa.us/public/pdf/BPR_pdf_files/Maps/Statewide/Historic_OTMs/1989fr.pdf. Retrieved July 18, 2010.
- Rand McNally and Company (1997). Easy-to-Read Travel Atlas: United States – Canada – Mexico (Map). p. 44. ISBN 0-528-81575-X.
- Hamill, Sean D. (December 27, 2008). "Road Stirs Up Debate, Even on Its Name". The New York Times.
- Bock, Greg (November 25, 2008). "Long road for I-99 comes to end". Altoona Mirror. Retrieved July 18, 2010.
- Gibb, Tom (December 7, 2002). "I-99 segment gets environmental OK". Pittsburgh Post-Gazette. Retrieved July 19, 2010.
- Bock, Greg (December 18, 2007). "Long-awaited I-99 stretch opens". Altoona Mirror. Retrieved July 19, 2010.
- "Report of the Special Committee on U.S. Route Numbering to the Standing Committee on Highways". American Association of State Highway and Transportation Officials. May 31, 2003. Retrieved July 18, 2010.
- Clarke, Cheryl R. (September 22, 2009). "Groundbreaking held for last section of '15' north". Williamsport Sun-Gazette. Retrieved January 17, 2010.
- DeLorme (2007). Street Atlas USA (Map).
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