Trout Creek Pass

Trout Creek Pass sits at 9,346 ft on the Park-Chaffee county line, at the southern end of the Mosquito Range in San Isabel National Forest. US-24 and US-285 run together over the top, co-signed for the climb. The pass is the divide between two worlds: the open South Park basin and the South Platte headwaters to the east, and the Arkansas River valley around Buena Vista and Johnson Village to the west. The two highways split and merge near Johnson Village at the south end and around the Antero Junction and Hartsel area at the north end.

For a loaded truck, the work is the descent. The south and west side runs a sustained grade of roughly 5 percent dropping toward Johnson Village and Buena Vista, while the north and east approach off South Park is gentle. The grade itself is moderate, but US-285 is a corridor you cannot easily avoid, and it is one of only seven routes on Colorado's commercial Must Carry chain list. When the road closes, the official detour is long: US-24 to I-25 at Colorado Springs and up to I-70.

Most of the documented severe weather trouble on this stretch of US-285 happens on the South Park side, between Fairplay, Grant and Kenosha Pass, not on the Trout Creek grade proper. South Park is one of the coldest and windiest high basins in Colorado, and wind over snow has iced and closed the road there more than once. The Trout Creek grade itself is usually open all year and closes only in severe winter storms.

• Summit elevation is 9,346 ft, 2,849 m (Wikipedia, topographic figure; the highway sign differs by about 140 ft)
• South and west side grade is roughly 5 percent toward Buena Vista; the north and east approach off South Park is gentle (Wikipedia; dangerousroads.org)
• US-24 and US-285 run concurrently over the pass, splitting near Johnson Village and merging near the Antero Junction and Hartsel area (Wikipedia)
• US-285 is one of seven corridors on Colorado's commercial Must Carry chain list (CDOT)
• Must Carry season runs September 1 to May 31; statewide there are 130 chain stations and 1,400-plus centerline miles covered (CDOT, Oct 2025)
• The pass marks the divide between the South Park basin and South Platte headwaters on the east and the Arkansas River valley on the west, on the Park-Chaffee county line (Wikipedia)
• Antero Reservoir, on US-285 between Fairplay and Buena Vista, dropped to minus 50 F on Dec 30, 2020 (CBS Colorado, citing NWS)

Colorado's commercial Must Carry law applies to US-285 from September 1 through May 31. During that window, every commercial vehicle on this corridor must carry chains or an approved alternate traction device, whether or not snow is falling that day. The requirement holds statewide along the route regardless of current weather.

There is no published numeric threshold for when Trout Creek Pass itself closes. The descriptions are qualitative: the grade is usually open all year and closes only in really bad winter storms (Wikipedia; dangerousroads.org). When closures happen on this part of US-285, they are more often on the adjacent South Park segment near Fairplay, Grant and Kenosha Pass, driven by high wind, blowing snow and ice rather than snowfall alone. If CDOT escalates past the traction law to a passenger vehicle chain law, that is the last step before the highway closes outright, and the official detour runs US-24 to I-25 at Colorado Springs and up to I-70.

Trout Creek Pass was railroad country before it was a truck route. In 1879 the Denver, South Park and Pacific Railroad crossed the pass, giving Denver its first rail link to Leadville during the Colorado Silver Boom. In the 1890s the Colorado Midland built a competing line west from Colorado Springs to Leadville over the same pass. Because it arrived second, the Midland crossed over the Denver, South Park and Pacific at the summit, reportedly the only point where the two lines met.

Both railroads fell into disuse in the 1920s, and remnants of both grades are still visible on the pass today. The old narrow-gauge route left its mark on the modern road as well: between Bailey and Como, the US-285 corridor still follows the original Denver, South Park and Pacific grade (Wikipedia; Buena Vista Heritage; Chaffee County Times).