Woodland at the site of the Cowan Creek Circular Enclosure, located on a peninsula on the northern side of Cowan Lake at Cowan Lake State Park in Adams Township, Clinton County, Ohio, United States. Built by Adenan peoples but now so badly eroded that it cannot easily be seen, the enclosure is an important archaeological site and has been listed on the National Register of Historic Places.
Woodland at the site of the Cowan Creek Circular Enclosure, located on a peninsula on the northern side of Cowan Lake at Cowan Lake State Park in Adams Township, Clinton County, Ohio, United States. Built by Adenan peoples but now so badly eroded that it cannot easily be seen, the enclosure is an important archaeological site and has been listed on the National Register of Historic Places. Nyttend · Public domain

Cowan Lake State Park

State Park · Ohio · Ohio Department of Natural Resources

Cowan Lake State Park is a 1,775-acre state park in southwestern Ohio, near Wilmington, built around a 700-acre lake with a 10-horsepower limit that keeps things quiet for paddlers and sailors. The Ohio Department of Natural Resources manages the park, which combines 1,075 acres of land with the lake's water acreage for a mix of swimming, fishing, boating, camping, and trail use.

It suits visitors looking for a low-key lake destination rather than a wilderness escape: families with a 1,000-foot beach and campground amenities, anglers working the lake or the youth fishing pond, and paddlers or sailors drawn to the lake's inlets and wooded shoreline. A seasonal Nature Center in the campground and an on-site historic earthwork add some variety for visitors who want more than water recreation.

Plan your visit

Camping & lodging

39 mapped camping locations

Site types & reservations: see the official site.

Know before you go

Address
1750 Osborn Road, Wilmington, OH, 45177
Phone
(937) 382-1096
Official site
ohiodnr.gov
Managed by
Ohio Department of Natural Resources
Hours
6am to 11pm daily. Visitors are permitted to actively engage in legitimate recreational activities outside these hours. If you have questions, call the park office.

Getting there

1750 Osborn Road, Wilmington, OH, 45177

Directions on Google Maps →

On the ground

The lake itself organizes the park, its shoreline broken into inlets that the state agency describes as scenic and wooded. ODNR maintains more than 8 miles of hiking trails around the property, including short loops such as Beechnut and Lakeview within the campground and Dogwood and Oldfield near the main office; the longer Spillway trail runs along the south side of the lake toward the park's Spillway, listed among its historic features. A separate half-mile Storybook Trail presents a children's story in segments for younger visitors.

The park's deeper history predates the lake itself. Two thousand years before American settlers reached what is now Clinton County, the Adena culture built earthworks in the area, including a circular enclosure and several mounds. In 1949, Raymond S. Baby of the Ohio History Connection and Ohio State University excavated one of the mounds, uncovering a ring of postholes 45 feet in diameter along with charred bark thought to be roofing material. That mound site was submerged when Cowan Lake was filled in 1950, but the circular enclosure survives on park grounds, its low profile making it hard to locate today.

Photos

Practical notes

Park hours run 6am to 11pm daily, with visitors permitted to continue legitimate recreational activities outside those hours. The park office can be reached at (937) 382-1096, and the park is located at 1750 Osborn Road, Wilmington, OH, 45177.

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88 parks mapped in Ohio

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Sources: State agency, Wikimedia Commons / editorial, OpenStreetMap contributors, USGS PAD-US, Google Places · updated 2026-08-12