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.

Chambersburg is a borough in and the county seat of Franklin County, in the South Central region of Pennsylvania, United States. It is in the Cumberland Valley, which is part of the Great Appalachian Valley, and 13 miles (21 km) north of Maryland and the Mason-Dixon line and 52 miles (84 km) southwest of Harrisburg, the state capital. According to the United States Census Bureau, Chambersburg's 2020 population was 21,903. When combined with the surrounding Greene, Hamilton, and Guilford Townships, the population of Greater Chambersburg is 52,273 people. The Chambersburg, PA Metropolitan Statistical Area includes surrounding Franklin County, and in 2010 included 149,618 people.