State Line is an unincorporated community and census-designated place in Antrim Township, Franklin County, Pennsylvania, United States. It is next to the Maryland state line along Interstate 81 and U.S. Route 11 between Hagerstown, Maryland, and Greencastle. As of the 2020 census the population was 2,804. State Line was originally called Middleburg, and under the latter name laid out in 1812, and named for its location between Greencastle and Hagerstown, Maryland.