U.S. Route 1 Alternate (US 1 Alt.) is an alternate route of US 1 in the U.S. state of Maryland. The highway runs between intersections with US 1 in Arbutus and in Baltimore. US 1 Alt. serves the southwestern Baltimore County community of Halethorpe and connects US 1 with full-access interchanges with Interstate 95 (I-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 DC 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 in southwest Baltimore. US 1 Alt. was created in 1949 when US 1 was moved to its present course through Arbutus and southwest Baltimore. The alternate route's interchanges with I-695 and I-95 were constructed in the late 1950s and mid-1970s, respectively. Route description US 1 Alt. begins at a partial interchange with US 1, which heads north as Southwestern Boulevard through Arbutus and south as Washington Boulevard toward Elkridge. There is no access from southbound US 1 Alt. to northbound US 1 or from southbound US 1 to northbound US 1 Alt. US 1 Alt. heads northeast as Washington Boulevard, a four-lane undivided highway that immediately crosses over Amtrak's Northeast Corridor railroad line, which carries MARC Train's Penn Line, and Herbert Run. The highway passes through Halethorpe, where the route temporarily expands to a divided highway through its three-ramp partial cloverleaf interchange with I-695 (Baltimore Beltway). There is no ramp from eastbound I-695 to US 1 Alt.; that movement is made via a ramp from eastbound I-695 to Sulphur Spring Road, which intersects US 1 Alt. at the I-695 junction, at the I-95–I-695 interchange to the west. US 1 Alt. continues northeast to an intersection with Caton Avenue and Hammonds Ferry Road just south of the Baltimore city limits. The alternate route leaves Washington Boulevard to turn north onto four-lane divided Caton Avenue and enters the independent city. US 1 Alt. then meets the western end of Patapsco Avenue at a directional intersection from which the latter avenue heads southeast. There is no direct access from Patapsco Avenue to the southbound