Interstate 78 in Pennsylvania

Interstate 78
I-78 highlighted in red
Route information
Maintained by PennDOT and DRJTBC
Length	77.95 mi[1] (125.45 km)
Existed	1957–present
History	Completed in 1989
NHS	Entire route
Major junctions
West end	I-81 in Union Township
Major intersections	US 22 from Bethel Township to Upper Macungie Township PA 501 in Bethel PA 183 near Strausstown PA 61 near Hamburg PA 100 in Fogelsville PA 309 from Dorneyville to Summit Lawn US 222 / PA 222 near Dorneyville PA 29 near Allentown PA 33 in Lower Saucon Township
East end	I-78 at the New Jersey state line in Williams Township
Location
Country	United States
State	Pennsylvania
Counties	Lebanon, Berks, Lehigh, Northampton
Highway system
Interstate Highway System Main Auxiliary Suffixed Business Future Pennsylvania State Route System Interstate US State Scenic Legislative
← PA 77 → PA 78
← PA 177 I-178 → PA 178

Interstate 78 (I-78) is a major east–west Interstate Highway stretching from Union Township, Lebanon County, Pennsylvania, in the west to the Holland Tunnel and New York City in the east. In Pennsylvania, I-78 runs for about 78 miles (126 km) from the western terminus at I-81 in Union Township east to the New Jersey state line near Easton in Northampton County.

Much of I-78 west of Allentown predates the Interstate Highway System as a freeway upgrade of U.S. Route 22 (US 22), which runs concurrently with I-78 between Bethel Township and Upper Macungie Township. The Interstate, originally planned as Interstate 80N (I-80N), was supposed to continue its concurrency with US 22 to the New Jersey state line but was realigned to the south due to local opposition.

Two auxiliary routes, Interstate 178 (I-178) and I-378, were also planned as spurs into Allentown and Bethlehem respectively, but I-178 was never built and I-378 became Pennsylvania Route 378 (PA 378) since it no longer connected to I-78. Improvement of the highway in Berks County is currently underway.