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.
The north terminus of US 3 is at a border crossing leading to Chartierville, Quebec. Since there is no town nearby on the American side, US 3 is often described as ending in Connecticut Lakes, New Hampshire. This is the name applied to the state forest that protects the upper reaches of the Connecticut River, where a chain of lakes is situated near its source. US 3 goes right past three of them: