Disappearing Routes

In researching the original path of US 6, it's become quite common for me to find that the roadway has vanished. In some cases, such as in Downtown Burbank, California, it's been redeveloped as a shopping mall, while in other cases, re-routing and freeway construction have left the original segments broken. In Dillon, Colorado, however, US 6's original path is underwater.
It's relatively common in the US to find a road that's been covered by a man-made lake. Typically, roads (and railroads) follow the easiest paths, which tend to be along rivers and creeks. When those rivers and creeks are dammed to form reservoirs, the roads must be moved. However, just because the highway is relocated, the pavement typically stays, often forming a natural boat ramp. A great example of this is around the shores of Amistad Reservoir in Southwest Texas. The original paths of US 90 and US 287 both are clearly visible still, even with the pavement markings. The dry climate has preserved it well.
In 1961, Dillon Reservoir was filled to supply water for the growing City of Denver. The reservoir sits directly on top of what was, until that point, the town of Dillon, Colorado. Denver Water Company, responsible for the construction of the dam, had been buying up the land under what is now the reservoir since the 1910's, accelerating in the 1930's during the Great Depression by simply paying the back property taxes on a parcel and forcing the residents out. Several buildings were moved, and the rest was partially bulldozed and partially scorched before receiving the 3,233 acres of water.
US 6 originally followed the Snake River into Dillon from the east, intersected State Route 9 in the middle of town, and joined it to follow Tenmile Creek SSW to Frisco. Today, the majority of this routing is underwater. As far as I can tell, the former routing leaves the current routing as Swan Mountain Road (Summit County Road 1) between Dillon and Keystone, goes for approximately 1700', then Swan Mountain Road takes a slight turn to go on a causeway over a piece of Dillon Reservoir. On Google Maps, a trail can be seen just south of the current US 6, which continues along Swan Mountain Road as it turns off. That's an old narrow gauge railroad bed (see the topo map below) that's been turned into a bike path.

Near the right center of the satellite view below, just above the roadway, a piece of the former US 6 grading can be seen as it descends into Dillon Reservoir:


The images below are of a USGS topo map, originally from 1934, surveyed in 1929, and re-printed in 1944. Overlayed onto that is a USGS topo map from 2013. The maps do not match exactly, but this is likely due to the surveying technology of the early 20th century. Being that there was no GPS then, the fact that it came out to be this close is a bit of a marvel, but you do have to use your imagination a bit.
The first topo overlay is of the area in the modern satellite image above, showing US 6's departure from its original route and descent into what is now Dillon Reservoir.

In the next topo overlay, looking at curves in the road as well as the names of creeks, you can determine where the existing roadway diverges from the original roadway shown here. At the north end, Straight Creek is visible, which still exists in present day Dillon. State Route 9 still takes an eastern turn to span the creek before heading south, though the Interstate 70 interchange currently exists just after this. It's very likely that the original roadway is now River Road, which dead-ends just north of the dam. I've marked approximately where the current State Route 9 diverges from the original route, as well as approximately where River Road (former State Route 9) ends today. Note that the former State Route 9 drives right into what is today Dillon Dam.

Looking at the western portion of the former US 6 route in the area, the old route is now underwater just east of what is today the downtown portion of Frisco. Just east of what is today State Route 9, the former US 6 route, Main Street in Frisco, dead-ends in a parking lot for a marina. At the lakeshore though, there's what appears to be the old road grade descending into the water. Note that the modern State Route 9 shown in red on the modern map did not exist before the lake was created, as it ran directly through Dillon and continued on a straight route, mostly following Miners Creek (which today exits from the lake near where SR 9 joins its former routing).

A modern satellite image of the area:

And, drawing a line from today's Main Street in the direct course the road took at the time the lake was flooded, it appears this is where the roadway lies.

I'm currently working on verifying all of this. I'm going to contact the Frisco Historical Society and, when I get to the area, walk to where I believe the old road grades to be, as well as try to come up with some maps that may better show where the modern lake met the former highways.