 In 1926, the U.S. Route 121 designation was applied to the whole length of SR 15, from North Carolina to Fort Chiswell, but it did not turn west on U.S. Route 11 at Fort Chiswell to connect to U.S. Route 21.An extension of SR 15 from Fort Chiswell north to Max Meadows was added to the state highway system in 1931.In the 1933 renumbering, SR 15 was dropped from the US 121 concurrency, while the short extension to Max Meadows became State Route 121.