History of the old highway along the Colorado River
At the time of this writing, it has been 50 years since the US 24 designation was cancelled between Grand Junction and Minturn, CO, leaving only US 6 along that stretch. Nevertheless, some locals (particularly along the segment around Glenwood Springs, New Castle, Silt, and Rifle) still refer to the old road as "Highway 6 & 24".
All of that brings up an important point: the US route system was not a program to build new highways. Rather, it was originally an initiative to identify the existing roads in each state that were the most important and most useful to interstate travelers. Once those roads had been identified, they were assigned numbers that carried through from state to state, and they were signposted with a special shield that was consistent throughout the states. The idea was to make it less confusing for people who wanted to drive from state to state without losing their way as they tried to navigate across the country.
In 1925, when the US route system was being planned, the state of Colorado requested several of their state highways to be included in the system, and one of them was State Highway 4, this road between Grand Junction and the Springs. The organization that would be administering the US highway system was the American Association of State Highway Officials (or AASHO), and they granted CDOT's wish later that year. But initially, this highway along the Colorado River was not given the designation of US 6 or US 24. Rather, in the 1925 planning stage, the thought was to designate this highway as US 46:
In 1935 the solution they came up with was that they would extend the US 24 designation west from Kansas City and have it absorb one of the US 40s. Heading west from Limon, they decided to have US 24 replace the southern US 40. So at that point the route connecting the Springs and Grand Junction was changed from US 40-South to US 24:
It should be noted that some people at the time were not happy about that. Why? US 40 was a coast-to-coast highway, running between San Francisco and Atlantic City. Even though US 40-South was sort of a spur highway that was separate from the transcontinental segment, some people still thought it was prestigious to be associated with a coast-to-coast highway number. US 24 on the other hand did not run from coast-to-coast; it went only as far east as Michigan. So even though changing the designation to US 24 was supposed to be less confusing for motorists, there were a lot of people in Colorado who viewed it as a loss that they no longer had the US 40-South designation.
In 1937, the US 6 designation was extended through Denver and west all the way to the Pacific coast near L.A. But at the time, Vail Pass did not exist, so there was no direct connection between Minturn and Copper Mountain. It was possible to use Shrine Pass, but even today that is a pretty rough route. So instead, from Copper Mountain (which was actually known as Wheeler at the time), US 6 traffic was directed south over Fremont Pass to Leadville, then north over Tennessee Pass to Minturn:
This meant that US 6 originally had a junction with US 24 at Leadville, so all the way from there to Grand Junction, the highway now had two numbers: US 6 and US 24. Shortly after that, Vail Pass was completed in about 1940, so then US 6 met US 24 at Minturn, and those two routes were dual-signed from there to Grand Junction.
Now (you might ask) why was that necessary? Couldn't they just end US 6 at Minturn, and instead extend US 24 west from Grand Junction to California? Well, yes, but the reason they didn't do that goes back to something we touched on above: people were very interested in transcontinental highways. If there was a highway that went all the way from the Atlantic to the Pacific, the expectation was that any town along that highway would have lots of tourists, and therefore they would have a greater shot at economic prosperity. Heading east, US 6 went all the way to Cape Cod on the Atlantic coast. So there were a lot of economic boosters who wanted to see US 6 extended west all the way to the Pacific. If instead it had been US 24 that was extended to the Pacific, then neither US 24 nor US 6 would have been transcontinental. So that's why US 6 was extended, and because of that we had this dual route -- US 6 and US 24 -- going through western Colorado, and that arrangement lasted for almost four decades.
Fast forward to the 1960s and '70s, when Interstate 70 was being built through Colorado. On the Western Slope, CDOT was not thrilled about the idea of signposting the new freeway with three different numbers, because they believed it would be confusing for motorists to see the highway marked as I-70, US 6, and US 24. So they asked AASHO (which by then was actually known as AASHTO) to truncate US 24 at Minturn, and in 1975 permission was granted:
But the funny thing is, that dual designation of 6&24 lasted so long that it became sort of ingrained in the minds of people on the Western Slope, and in some ways it has endured even up to the present day.
Gabe Chenoweth, General Manager of KMTS(FM) in Glenwood, was curious about that, so he did some searching online and found the usends.com website. Since he is also the host of a long-form interview program, he reached out to me and asked if I would be interested in discussing that subject on the air. I agreed, and we did the interview on Sep. 29, 2025. If you'd like to hear it, please visit this page.
To prepare for that interview, I did a fair amount of research, but as it turned out, there wasn't enough time in the program to include all of the material. Not wanting that effort to go to waste, I decided to post all of my notes here (in consideration of the radio station's audience, this material primarily focuses on the Garfield County portion of the route).
To prepare for that interview, I did a fair amount of research, but as it turned out, there wasn't enough time in the program to include all of the material. Not wanting that effort to go to waste, I decided to post all of my notes here (in consideration of the radio station's audience, this material primarily focuses on the Garfield County portion of the route).
Relics of old US highway 6 & 24 along what is now the Glenwood Canyon recreational trail between Glenwood Springs and No Name.
If we were to say "the highway that runs along the Colorado River" most people would probably assume we were referring to I-70. But of course it wasn't always that way. The interstates didn't begin construction until the 1960s (and I-70 through Glenwood Canyon actually wasn't finished until the 1990s). But the focus of my website is the highways that people used before the Interstates existed, or more specifically, the US highways. Those have been around since 1926, so about three decades prior to the Interstates. And in this particular article, we will briefly go even a little farther back than that.
The first road to be constructed along the Colorado River was actually the railroad; it was completed in the late 1800s. Right around the turn of the century is when more and more people started driving automobiles, and it was 1902 when the first automobile road was completed west from Grand Junction and over the mountains. It was called the Taylor State Road, and we can refer to that as the first "highway" through the area, even though it was unpaved and it was nothing like what we think of today when we use the word "highway".
So this road along the Colorado River existed about a quarter-century before the US route system was implemented, and during those years this highway also had a few other designations. Around 1913 it became a segment of the Midland Auto Trail. Around 1916, when CDOT (or actually CDOT's predecessor) started numbering their state highways, they initially designated the Colorado River road downstream from Glenwood as State Highway 11, while upstream was State Highway 10 (shown on their 1916, '19, '21, and '22 maps). It is unknown whether these roads were actually signposted that way, but regardless, in about 1923 the Colorado River road was changed to State Highway 4.
The first road to be constructed along the Colorado River was actually the railroad; it was completed in the late 1800s. Right around the turn of the century is when more and more people started driving automobiles, and it was 1902 when the first automobile road was completed west from Grand Junction and over the mountains. It was called the Taylor State Road, and we can refer to that as the first "highway" through the area, even though it was unpaved and it was nothing like what we think of today when we use the word "highway".
So this road along the Colorado River existed about a quarter-century before the US route system was implemented, and during those years this highway also had a few other designations. Around 1913 it became a segment of the Midland Auto Trail. Around 1916, when CDOT (or actually CDOT's predecessor) started numbering their state highways, they initially designated the Colorado River road downstream from Glenwood as State Highway 11, while upstream was State Highway 10 (shown on their 1916, '19, '21, and '22 maps). It is unknown whether these roads were actually signposted that way, but regardless, in about 1923 the Colorado River road was changed to State Highway 4.
All of that brings up an important point: the US route system was not a program to build new highways. Rather, it was originally an initiative to identify the existing roads in each state that were the most important and most useful to interstate travelers. Once those roads had been identified, they were assigned numbers that carried through from state to state, and they were signposted with a special shield that was consistent throughout the states. The idea was to make it less confusing for people who wanted to drive from state to state without losing their way as they tried to navigate across the country.
In 1925, when the US route system was being planned, the state of Colorado requested several of their state highways to be included in the system, and one of them was State Highway 4, this road between Grand Junction and the Springs. The organization that would be administering the US highway system was the American Association of State Highway Officials (or AASHO), and they granted CDOT's wish later that year. But initially, this highway along the Colorado River was not given the designation of US 6 or US 24. Rather, in the 1925 planning stage, the thought was to designate this highway as US 46:
(Excerpt from the 1925 report to the Secretary of Agriculture from the Joint Board on Interstate Highways)
But then, in Sept. 1926, just a couple months before the US routes were officially established, the US 46 designation was cancelled, and instead the route was designated as a westward extension of US 40 South. The west beginning was at Grand Junction, and from there US 40-South went up the Colorado River through Rifle and Glenwood. At Dotsero it left the Colorado River and continued eastward by going up the Eagle River. At Minturn it went south through Leadville to Buena Vista, and then east again through the Springs and on into Kansas:
(Excerpt from AASHO's 1927 route log)
The reason this highway was designated US 40-South was to differentiate it from the regular US 40, which is the route that runs through Steamboat, Craig, and so on. So in other words there were two US 40's, a northern and a southern US 40. It didn't take AASHO very long to realize that this arrangement with two US 40s was confusing to motorists. So they started working with CDOT to come up with a way to renumber one of the US 40s.
In 1935 the solution they came up with was that they would extend the US 24 designation west from Kansas City and have it absorb one of the US 40s. Heading west from Limon, they decided to have US 24 replace the southern US 40. So at that point the route connecting the Springs and Grand Junction was changed from US 40-South to US 24:
(Excerpt from a 1935 letter from AASHO to the DOTs of Kansas and Colorado)
It should be noted that some people at the time were not happy about that. Why? US 40 was a coast-to-coast highway, running between San Francisco and Atlantic City. Even though US 40-South was sort of a spur highway that was separate from the transcontinental segment, some people still thought it was prestigious to be associated with a coast-to-coast highway number. US 24 on the other hand did not run from coast-to-coast; it went only as far east as Michigan. So even though changing the designation to US 24 was supposed to be less confusing for motorists, there were a lot of people in Colorado who viewed it as a loss that they no longer had the US 40-South designation.
Today this 1937 steel bridge at the Shoshone Dam is partially obscured by newer wood and chain-link fences. It is now used to connect traffic between I-70 and the Hanging Lake trailhead. But before I-70 was built, this bridge served as US 6 & 24, carrying both directions of highway traffic through Glenwood Canyon. The plaque on the bridge is shown in the photo below.
In 1937, the US 6 designation was extended through Denver and west all the way to the Pacific coast near L.A. But at the time, Vail Pass did not exist, so there was no direct connection between Minturn and Copper Mountain. It was possible to use Shrine Pass, but even today that is a pretty rough route. So instead, from Copper Mountain (which was actually known as Wheeler at the time), US 6 traffic was directed south over Fremont Pass to Leadville, then north over Tennessee Pass to Minturn:
(Excerpt from a 1937 letter from CDOT to AASHO)
This meant that US 6 originally had a junction with US 24 at Leadville, so all the way from there to Grand Junction, the highway now had two numbers: US 6 and US 24. Shortly after that, Vail Pass was completed in about 1940, so then US 6 met US 24 at Minturn, and those two routes were dual-signed from there to Grand Junction.
Now (you might ask) why was that necessary? Couldn't they just end US 6 at Minturn, and instead extend US 24 west from Grand Junction to California? Well, yes, but the reason they didn't do that goes back to something we touched on above: people were very interested in transcontinental highways. If there was a highway that went all the way from the Atlantic to the Pacific, the expectation was that any town along that highway would have lots of tourists, and therefore they would have a greater shot at economic prosperity. Heading east, US 6 went all the way to Cape Cod on the Atlantic coast. So there were a lot of economic boosters who wanted to see US 6 extended west all the way to the Pacific. If instead it had been US 24 that was extended to the Pacific, then neither US 24 nor US 6 would have been transcontinental. So that's why US 6 was extended, and because of that we had this dual route -- US 6 and US 24 -- going through western Colorado, and that arrangement lasted for almost four decades.
Fast forward to the 1960s and '70s, when Interstate 70 was being built through Colorado. On the Western Slope, CDOT was not thrilled about the idea of signposting the new freeway with three different numbers, because they believed it would be confusing for motorists to see the highway marked as I-70, US 6, and US 24. So they asked AASHO (which by then was actually known as AASHTO) to truncate US 24 at Minturn, and in 1975 permission was granted:
(Excerpt from CDOT's 1975 application to AASHTO)
But the funny thing is, that dual designation of 6&24 lasted so long that it became sort of ingrained in the minds of people on the Western Slope, and in some ways it has endured even up to the present day.
From a hillcrest on the old US 6 roadbed, along the west side of Vail Pass (I-70 is visible in the distance, as is part of the Vail Pass bike trail). From this point, heading this direction (eastbound), the old highway has been repurposed as a runaway truck ramp, and beyond there, I-70 now sits on top of old US 6. The view to the opposite direction (westbound) is visible in the next photo.
From the same vantage point as the photo above, heading the opposite direction (westbound). Old US 6 is still paved up to the turnaround visible in the distance (where the biker is). This segment is no longer open to motor vehicles, so perhaps the best way to see it is via bike.
A few other notable milestones:
- Prior to about 1930, there was no road through DeBeque Canyon. So drivers heading west from Glenwood or Rifle could follow the river only as far as the town of DeBeque. From there motorists had to leave the river and take the long way around the canyon, first by going south to the town of Mesa, and then west along Plateau Creek to its junction with the Colorado River near Palisade.
- Some segments of the highway were first paved during the mid-30s; prior to that it was an entirely gravel road.
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