I-81 enters Pennsylvania at the Maryland state line about south of Chambersburg. In Chambersburg at exit 16, it meets U.S. Route 30. About a mile north of Carlisle at exit 52, it meets U.S. Route 11, which takes passengers to the Pennsylvania Turnpike/ Interstate 76, since I-81 has no direct interchange with I-76. The stretch of US 11 connecting I-81 to I-76 is known locally as the "Miracle Mile" since it contains plenty of traveler services including restaurants, gas stations, lodging, truck stops, shops, etc. From here, I-81 travels in an almost precisely east-west direction for the next 37 miles. At exit 59, it has an interchange with the western terminus of Pennsylvania Route 581. I-81 becomes the Capital Beltway from exit 59 to exit 70. As passengers approach exit 67, a major complex interchange is seen. The interchange consists of U.S. Route 22 and U.S. Route 322; U.S. Route 322 merges with Interstate 81. Exit 70 is the eastern terminus of the US 322 concurrency and the northern terminus of Interstate 83, and is located in Colonial Park. For the entire segment between the Mason–Dixon line and Interstate 78, I-81 runs through the Great Valley. North of Harrisburg between Interstate 83/U.S. Route 322 and Interstate 78, the highway passes near Hershey and Fort Indiantown Gap. At mile marker 89, I-81 meets the western terminus of I-78, I-78 picks up the eastward route through the Great Valley and heads toward Allentown and New York City, while I-81 turns back northward, cutting through the Blue Mountain at Swatara Gap. From mile marker 141 to mile marker 146, I-81 passes near the city of Hazleton. At exit 151, I-81 meets Interstate 80. As motorists enter Wilkes-Barre at mile marker 165, Interstate 81 merges with Pennsylvania Route 309 for. At exit 175, I-81 meets with Pennsylvania Route 315, which will lead passengers to the Northeast Extension of the Pennsylvania Turnpike. In Scranton at mile marker 185, there is a short freeway called the Central Scranton Expressway, which will lead passengers into downtown Scranton. At mile marker 187, I-81 is at the Throop Dunmore Interchange, which consists of Interstate 84, Interstate 380, and U.S. Route 6. US 6 merges with I-81 for from mile marker 187 to mile marker 194. At mile marker 194 is the northern terminus of Interstate 476 and the Northeast Extension of the Pennsylvania Turnpike. The last exit in Pennsylvania is exit 230, which is Pennsylvania Route 171 near Hallstead. north of exit 230 is the New York state line.
History
A toll highway along the present-day I-81 corridor through Pennsylvania was planned in the 1950s. The section from Scranton to the New York State line was planned as a continuation of the Northeast Extension of the Pennsylvania Turnpike. A new extension of the turnpike Between Harrisburg and Scranton was also proposed. After the Federal Aid Highway Act of 1956 was passed, plans were changed to build a freeway rather than a toll road. The first section to be built ran from PA 347 in Dunmore to US 11 in northern Scranton, this section opening in 1960. All of I-81 in Pennsylvania was completed by the 1970s. Construction cost nearly $443 million. On May 9, 2013, a tanker crashed and caught fire at the interchange between I-81 and US 22/US 322 in Harrisburg. The fire damaged the bridges carrying westbound US 22/US 322 and a ramp over I-81. At least one of those bridges, carrying US 22 eastbound over I-81 and several ramps, and possibly another, the ramp carrying traffic from I-81 northbound to US 22/US 322 westbound, would have to be demolished and replaced. The fire resulted in about ten miles of I-81 being closed in both directions, with traffic being diverted along the southern portion of the Capital Beltway. The highway would not be fully reopened to traffic until the evening of May 13.
Future
Scranton Beltway
On April 28, 2016, plans were announced for a Scranton Beltway to use the Pennsylvania Turnpike Northeast Extension as a bypass for I-81 around the heavily congested segment through Scranton and its suburbs. The turnpike between the two I-81 interchanges carries an average of 10,000 vehicles per day vs. 80,000 on the parallel segment of I-81. This project will build two high-speed connections between I-476 and I-81: one south of Scranton in Dupont and one north of Scranton in South Abington Township. Tolls on the connections will be paid with E-ZPass or toll-by-plate. Construction on this project, which is expected to cost $160 million, could begin as soon as 2021.
New interchange in Chambersburg
On October 24, 2018, PennDOT released their plans for a new exit 12 on I-81, at Guilford Springs Road, estimated to cost around $23 million. The purpose for the exit is to improve access for trucks to the various distribution warehouses south of Chambersburg, such as Target. As such, Guilford Springs Road will be widened to three lanes as a part of this project. PennDOT has started obtaining environmental clearances and will start to seek rights of way in 2020 from approximately 7-10 properties. PennDOT will look at bids for construction starting in 2023.
