Highway was the main north/south thouroghfare through Austin in the 1920s and 1930s. At some point in the late 30s or early 40s, it was renamed Highway 81. Highway 81 was also referred to as the "Dallas Highway".
Part of Highway 81 north of Austin became Interstate 35 in 1954. The part of Highway 81 that was in Austin separate from I35 was renamed Lamar Blvd.