US 1, which have 12 lanes over four carriageways, have a partial cloverleaf interchange with Clark Street and Boundary Channel Drive and another interchange with the George Washington Memorial Parkway before the two highways cross the Potomac River into the District of Columbia on the 14th Street bridges complex. History What is now US 1 was added to the state highway system in 1918 as State Route 1 (SR 1), following the older Jefferson Davis Highway, which approximated at its northern end the route of the former Washington and Alexandria Turnpike. The road was renumbered State Route 31 (SR 31) in the 1923 renumbering, and US 1 was applied to its whole length in 1926. SR 31 was dropped in the 1933 renumbering and was immediately reused on its current alignment. Prior to , SR 1/SR 31 crossed the North Carolina state line with SR 2/SR 32 south of Clarksville on present US 15. On the North Carolina side, it was North Carolina Highway 75 (NC 75). From Clarksville, it ran east on present US 58 to near South Hill. The route continued east from South Hill to Edgerton on present US 58 and north to near McKenney on present SR 712 until about the same time. This alignment was defined as the Jefferson Davis Highway on March 17, 1922. By 1925, SR 31 was moved to the current alignment of US 1 south of McKenney (previously State Route 122 [SR 122] south of South Hill and State Route 314 [SR 314] north of South Hill), but the Jefferson Davis Highway did not follow. This took SR 31 to the border at what was then NC 50. The old alignment remained SR 32 south of Clarksville and SR 12 from Boydton to Edgerton and became SR 201 from Clarksville to Boydton and a new SR 122 from Edgerton to near McKenney. The preliminary plan for U.S. Numbered Highways was drawn up in 1925, and all of SR 31 was assigned US 1. The former SR 31 west and south from near South Hill into North Carolina became US 401. In late 1926, the final plan was adopted, and all of US 401 was renumbered to US 15. However, by April 1927, US 15 had been extended north from Clarksville, and the short piece from Clarksville to near South Hill was again US 401. In 1975, the interchange between I-395 and