The valley is mostly underlain by Paleozoic and Mesozoic sedimentary rocks concealed by a thin[quantify] layer of gravel laid down by glaciation during Pleistocene time.

Red Hill runs through the center of the valley as a hogback ridge of tilted Cretaceous and Jurassic sedimentary rocks.

On its southwestern side, at the southern end of the Mosquito Range, it is connected by Trout Creek Pass to the upper valley of the Arkansas River near Buena Vista.

However, from the 1850s onward, the area was increasingly encroached on by Southern Arapaho bands, who came to cherish it as an important buffalo range after witnessing the continued degradation of their typical hunting grounds on the plains and who repeatedly became entangled in skirmishes with the Utes over the territory.

It was explored by John C. Fremont during his second expedition in 1844, at which time it was referred to as "Bayou Salade", a corruption of Spanish "Valle Salado", meaning salty valley.

South Park City, an open-air museum outside Fairplay, provides a historical recreation of the gold rush days.

Trey Parker, one of the creators of the South Park series, grew up in Conifer, about 40 miles (65 km) east of Fairplay.