The access road to Thirtymile Campground and Rio Grande Reservoir turns off from SH149 either 20.5 miles west from Creede or 32 miles south from Lake City. The turnoff is marked by a road sign. From Lake City, you'll have to drive over Slumgullion Pass and Spring Creek Pass. This remote access for Rio Grande Pyramid and other 13er summits nearby makes these peaks some of the most distant for climbers coming from both the eastern and western slopes of Colorado, requiring multiple hours of driving.
Watch for FR520/CR18 turning off to the west side of highway 149. Initially, the road is paved as it drops down to a small reservoir where it turns NNW and turns to graded dirt. Shortly after that, stay left at an intersection. For the most part, stay on the most well-travelled road to get to Rio Grande Reservoir. Most major intersections are signed. So at about 3.5 miles from the highway, stay left and head south. In the next mile you'll come to Road Canyon Reservoir #1 where there is a National Forest Fee campground along the side of the road at the south end of the reservoir with a vault toilet and a half dozen sites or so. Continue on past the River Hill CG another 3.4 miles SW and then you'll arrive at the Thirtymile CG at 10.8 miles from the highway. Both Thirtymile and River Hill campgrounds are also Forest Service, fee campgrounds with vault toilets, tables, firerings and potable water. Sites can be reserved at www.recreation.gov.
To access the campground, you'll need to drive south across the river on a good bridge. There's a grassy/dirt parking area intended for backpackers and hikers on the north side of the main road into the campground. For the actual trailhead, you'll need to walk south from the parking area, crossing the other side of the road that loops through and then walk a little farther south from there. The trailhead serves as access for both Squaw Creek and Weminuche Creek. There is a kiosk there for registering your activity.