Interstate 81 (I-81) is a north–south Interstate Highway, stretching from Dandridge, Tennessee, northeast to Fisher's Landing, New York, at the Canada–United States border. In Pennsylvania, I-81 runs for 232.76 miles (374.59 km) from the Maryland state line northeast to the New York state line near Hallstead and is called the American Legion Memorial Highway. The interstate enters the state near the borough of Greencastle, serving the boroughs of Chambersburg and Carlisle, before reaching Harrisburg, the capital. After that, it climbs into the Pocono Mountains to run through the Wyoming Valley, then exits into New York. It is the longest north–south Interstate in Pennsylvania.

Hallstead is a borough in Susquehanna County, Pennsylvania. The population was 1,179 at the 2020 census.