Pike and San Isabel National Forests · Colorado
Threemile
7.2 mi of trail, end to end · native material surface · trail No. 635 · trail class 3 · typical grade 12-20% · tread 18-24 inches wide · hiking, horse, bike
Campgrounds
Along the way Whiteside Picnic Area
Begins at the forest's mile 0, 39.4815, -105.6933 - no trailhead mapped Drive to where the trail begins
Geneva Creek Trailhead the Forest Service's write-up
The Geneva Creek Trailhead provides access to the Geneva Creek Trail (#697) , which travels upstream for approximately 3/4 miles to a junction with the Threemile Trail (#635) at the Threemile Trailhead/ Whiteside Picnic Area .
The Threemile Trail continues upstream along Geneva Creek from this point, approximately 1/2 mile further, before crossing the Guanella Pass Road and eventually entering the Mount Evans Wilderness.
This trailhead on fs.usda.gov
Every trail in Pike and San Isabel National Forests
About this trail's facts
The lines are the US Forest Service's National Forest System trails layer (public domain), read 2026-10-16 and simplified for the map; the length is the line's, end to end, and the class, surface, grade and tread width are the forest's own entries where it publishes them - a forest that publishes the centreline alone has none. The trailheads and the points along the way are the Service's recreation points, and the write-ups its own recarea text, unedited. Heights come from USGS 3DEP through Terrain Tiles on AWS (Mapzen/Tilezen), read along each line and rounded; a short trail on steep ground can be off by a few tens of feet. Closures change: check the forest's own site before you go.
