"One great red line"
For about a quarter-century, US Route 6 was the longest highway in the country. In Jack Kerouac's novel On the Road, the main character described it as "one great red line across America". During those years it ran between Provincetown MA and Long Beach CA, and I believe there has never been a longer highway in the United States. Exactly how long was it? Well, believe it or not, the answer to that question is debatable (see this page for more details about why it is difficult to calculate).
Shrine Pass was not considered to be a good candidate for development into a primary state highway, so US 6 traffic was directed further south from Copper Mountain, along today's SH 91. Drivers had to go over Fremont Pass and all the way down to Leadville. There, traffic was directed north (overlapped with westbound US 24) over Tennessee Pass and up to Minturn.