Fossil Butte National Monument

State: Wyoming. Type: National Monument (National Park Service) in Lincoln County, 15 miles west of Kemmerer. Size: 8,198 acres. Established as a national monument on October 23, 1972. Fee-free. Preserves 52-million-year-old freshwater lake fossils from the Eocene Green River Formation. 2025 visitation: 20,626.

Fossil Butte National Monument protects one of the world's richest deposits of fossilized freshwater lake life, preserved within the Green River Formation of southwestern Wyoming. The monument sits on the site of ancient Fossil Lake, a subtropical freshwater basin that existed roughly 52 million years ago during the Eocene Epoch and persisted for about two million years. Exceptional preservation conditions at the lake bottom captured fish, crocodiles, turtles, bats, early horses, insects, and plants in fine detail, making the site, in the National Park Service's description, among the best paleontological records of Cenozoic aquatic communities in North America. Visitors can view more than 80 fossils and fossil casts at the visitor center, hike monument trails, and in some cases join ranger-led fossil preparation demonstrations.

The monument is located in Lincoln County, in southwestern Wyoming, about 15 miles west of the town of Kemmerer. Its mailing address is P.O. Box 592, Kemmerer, WY 83101.

The monument experiences a high-elevation, semi-arid climate with cold winters (record low of -45°F) and warm summers (record high of 109°F). Average annual precipitation is about 11.72 inches, with roughly 76.5 inches of snowfall per year.

The scenic drive to the picnic area and Nature Trail is closed from November until late May, weather-dependent, so late spring through fall is the most reliable window for full access to trails; the visitor center itself operates on a modified schedule through the winter.

The monument preserves deposits from ancient Fossil Lake, the smallest of three great lakes that once made up the Green River Lake System during the Eocene Epoch (roughly 56-34 million years ago). Fossil Lake measured 40-50 miles long and 20 miles wide and persisted as a low, subtropical freshwater basin for about two million years, allowing fine-grained sediments to preserve fish, reptiles, mammals, birds, insects, and plants in exceptional detail. The site was designated a national monument and placed under National Park Service management on October 23, 1972.

Visitors can explore fossil exhibits and view more than 80 fossils and fossil casts at the visitor center, hike the monument's trails, drive the scenic road (seasonal), and take part in ranger-led programs, including fossil preparation demonstrations when offered. Distance-learning virtual field trips are also available through the park.

The visitor center houses the monument's main fossil exhibits. Outdoor features include hiking trails and a scenic drive that provides access to a picnic area and the Nature Trail, showcasing the butte formations and surrounding high-desert terrain that hold the fossil beds.

The monument is reached by road roughly 15 miles west of Kemmerer, Wyoming; specific airport and public-transit details were not confirmed from the sources reviewed, so visitors should plan on a personal or rental vehicle.

The visitor center is open daily 8:00 a.m.-4:30 p.m. in spring (May 1 through the Thursday before Memorial Day); daily 8:00 a.m.-5:30 p.m. in summer (Friday before Memorial Day through Labor Day); daily 8:00 a.m.-4:30 p.m. in fall (day after Labor Day through October 31); and Monday-Saturday 8:00 a.m.-4:30 p.m. in winter (November 1-April 30), with Sunday and select holiday closures. The scenic drive to the picnic area and Nature Trail is closed from November until late May, weather-dependent.

Fossil Butte National Monument is fee-free; an entrance pass is not required to access the site, per the National Park Service. The monument no longer issues interagency passes on-site; those are handled by the Bureau of Land Management office in Kemmerer.

A visit to the visitor center exhibits plus a short trail walk can be done in two to three hours; adding the full scenic drive and Nature Trail, when open, extends a visit to a half-day.

The nearby town of Kemmerer, about 15 miles from the monument, is the closest source of lodging; specific hotel names were not confirmed from the sources reviewed.

Dining options are concentrated in Kemmerer, the nearest town; the monument itself does not appear to operate food concessions based on the sources reviewed.

Kemmerer, the nearest town, and the surrounding Green River Formation badlands are the main related points of interest; more distant sites were not confirmed from the sources reviewed.

There is no on-site public transit; visitors typically drive to the monument from Kemmerer or elsewhere in southwestern Wyoming. Specific nearest-airport information was not confirmed from the sources reviewed.

Winters bring extreme cold (record low -45°F) and heavy snow, so check road and trail conditions before visiting outside the summer season. Standard hiking precautions (water, sun protection, sturdy footwear) apply on the monument's trails.

Water, sun protection, and layered clothing suited to a high-desert climate with wide temperature swings; sturdy footwear for the hiking trails.

Plan visits between late May and October for full access to the scenic drive, picnic area, and Nature Trail, since this route closes seasonally. Check the current visitor center hours before arriving, as they shift by season.

Dial 911 for any emergency. For general park information, Fossil Butte National Monument can be reached at 307-877-4455.

Fossil Butte National Monument (National Park Service) - https://www.nps.gov/fobu/index.htm

This section is being updated and will be available shortly.

This section is being updated and will be available shortly.

This section is being updated and will be available shortly.