Sioux County

The county in brief

A traveler's read on Sioux County

Roughly 19 million years ago a waterhole on what is now Sioux County's Niobrara River drainage dried abruptly and trapped a thousand-strong herd of Miocene-epoch grassland mammals — the bone bed exposed by University of Nebraska paleontologists in 1904 produced complete articulated skeletons of Menoceras (a small two-horned rhinoceros), Moropus (a clawed horse-relative), Stenomylus (a delicate gazelle-camel), and Daphoenodon (the bear-dog apex predator), and that single deposit is now Agate Fossil Beds National Monument, the only NPS unit in Nebraska preserving Miocene mammal-fossil beds. The visitor center's Cook Collection includes Plains Indian artifacts traded between James Cook and the Oglala chief Red Cloud during their decades-long friendship; the collection's provenance is one of the cleanest in any NPS museum per the NPS Foundation Document for AGFO.

Toadstool Geologic Park inside the surrounding Oglala National Grassland holds badlands-style erosion formations — Brule Formation siltstones eroded into pedestal-and-cap toadstool shapes — and the USFS-managed primitive campground there accepts rigs to 25 ft with no services, the canonical free public camp for this corner of the High Plains. Fort Robinson State Park 30 miles south (22,000 acres, Nebraska's largest state park, formerly a frontier-era US Army cavalry post where Crazy Horse was killed in a guardhouse incident on 5 September 1877) accepts rigs to 50 ft with full hookups, runs horseback trail rides, and operates a Buffalo Soldiers museum in the original 1909 brick stables. The Pine Ridge escarpment running across the county marks the northernmost extension of the Ogallala Aquifer outcrop and the bioclimate transition from short-grass prairie to ponderosa-pine savanna.