The first highway through Weldon Canyon was completed in 1930. The “Newhall Alternate” was the first major realignment of US 99 south of the Ridge Route. In 1949, passing lanes were added as a temporary measure from Tunnel Station to just north of Weldon Summit until the freeway could be constructed. In 1954, US 99 was upgraded to a freeway through here, ending south of the summit. North of the summit, the freeway merged with the 1951 expressway in Gavin Canyon. In 1968, the area was changed yet again, and in the most drastic way, as the roadway was rebuilt as Interstate 5.