Wyoming is a spectacular landscape of mountain ranges separated by broad basins. While most of the uplifts, including the Laramie, Medicine Bow, Wind River, Owl Creek, Bighorn, Absaroka and Teton Ranges, are well known to travelers, skiers, hikers and naturalists, a less obvious geologic uplift stretches across eastern Wyoming.
Known as the Hartville Uplift, this geologic arch connects the Laramie Range with the southwestern edge of the Black Hills, in South Dakota. Separating the structural Powder River Basin, to its north, from the Denver Basin, to its south, this subsurface ridge of Precambrian basement rock formed during the Laramide Orogeny, some 65 million years ago, when the Rocky Mountains crumpled skyward. Paleozoic and Mesozoic sediments lying above the arch were lifted as well, producing a broad ridge which has since been dissected by streams and buried by erosional debris from the mountains.
Today, evidence of the Hartville Uplift is provided by outcrops of Pennsylvanian and Permian strata amidst a sea of Cretaceous and Tertiary deposits. The Uplift branches from the Laramie Range in the vicinity of Glendo Reservoir (on the North Platte River) and angles to the northeast where it eventually merges with the Black Hills. Wyoming 270, between US 26 and US 20, is known as the Hartville Highway and runs through a large portion of the Hartville Uplift.
