Horsetooth Reservoir is a 6.5-mile-long mountain lake in the foothills just west of Fort Collins, surrounded by 1,900 acres of public land. People come for the boating, fishing, swimming, camping, cliff-lined coves and sunset views of Horsetooth Rock.

The reservoir was built in the late 1940s and early 1950s as part of the Colorado-Big Thompson Project, which carries Western Slope water under the Continental Divide to Northern Colorado farms and cities. Four earthen dams (Horsetooth, Soldier Canyon, Dixon Canyon and Spring Canyon) close off gaps in the hogback ridge to hold the water at an elevation of about 5,420 feet. Beneath the surface lies the old quarry town of Stout, whose sandstone helped build early Fort Collins. The Bureau of Reclamation and the Northern Colorado Water Conservancy District manage the water levels, and Larimer County manages the recreation. The lake takes its name from Horsetooth Rock, the tooth-shaped summit that rises above the west shore in Horsetooth Mountain Open Space.

The reservoir is open year-round. South Bay, at the south end, has the main campground, swim beach, group pavilion, boat ramp and the Horsetooth Area Information Center, and Inlet Bay to the west has a marina and a second campground. Anglers fish for walleye, smallmouth bass and trout. Paddleboarders and kayakers explore the quiet coves, and scuba divers, cliff climbers and cyclists on County Road 23 all share the shoreline. A daily entrance permit costs $10 per vehicle and is good for 24 hours. All boats need an aquatic nuisance species inspection before launching, so launches are limited to inspection hours. The information center is open 9 a.m. to 4 p.m. daily from March through October and Monday through Friday from November through February. The Inlet Bay boat ramp is closed for the season after October 18.

Check boat ramp hours, water conditions, camping availability and permit prices on the Horsetooth Reservoir page from Larimer County Natural Resources.