US6 (The Grand Army of the Republic Highway) was one of the original major highways running East/West through the United States. The highway starts at the tip of Cape Cod and extended westward. The 1926 designated highway ran from Provincetown (at the tip of Cape Cod) to Brewster, New York. The 1927 designated extended to Erie, Pa. The 1931 designation extended to Greeley (present day U38). In 1937, the highway dipped south through Denver, crossed the Continentental Divide snaked through Central Utah and Nevada. In Bishop, California, US6 joined present day U395 southward and became an official transcontinental highway by terminating at Long Beach, California...crossing 3157 miles.
US6 is unique in that it took a diagonal path across the country. NOTE, in 1964, California renumbered much of the route of US6. Today's maps show US6 terminating at Bishop, California.
Like most of the original highway system, US6 took a circuitous route through the country. It would divert north or south to visit pioneer towns or take long detours to avoid geological features like the San Raphael Swell or Sierra Nevada. Likewise, the road would often share designation with other highways. Much of the route followed by US is now served by I70 and I80.
Interstate 70 opted for the direct route. To make the route as straight as possible, engineers blasted tunnels through the Rockies and blasted a straight path through the San Raphael Swell.
US6 and I70 often cross paths. However, the old highway takes several diversions through towns missed by the Interstate.
Many portions of the highway were replaced by Interstate 70. Highway 6 took a much more circuitous