U.S. Route 1 Alternate (US 1 Alternate) is an alternate route of US 1 in the U.S. state of Maryland. The highway runs 3.92 miles (6.31 km) between intersections with US 1 in Arbutus and in Baltimore. US 1 Alternate serves the southwestern Baltimore County community of Halethorpe and connects US 1 with full-access interchanges with Interstate 95 and I-695. The Washington Boulevard portion of the alternate route was the original road southwest from Baltimore in the 18th century and was part of the turnpike southwest to Washington for much of the 19th century. The highway was paved in the early 1910s, expanded in the late 1910s and late 1920s, and became part of US 1 in 1926. The Caton Avenue portion of the alternate route was improved and expanded in the 1930s to serve as a rerouting of US 1