State Highway 5, or SH 5, runs along the old route of U.S. Highway 75 at Howe into the city of Allen. SH 5 parallels US 75 along its length and runs alongside the former Houston and Texas Central rail line. SH 5 was created in 1959 when the new route of US 75 was established to the west. Historically, SH 5 extended into and through Plano and Richardson.