Keyhole State Park in northeastern Wyoming centers on Keyhole Reservoir, a large impoundment on the Belle Fourche River created by the completion of Keyhole Dam in 1952. The reservoir was built not only for recreation but also for irrigation storage, flood and sediment control, fish and wildlife conservation, and municipal and industrial water supply. Its water is shared by interstate compact, with most allocated to South Dakota and the rest to Wyoming, tying it to the broader Belle Fourche basin system. Today the area serves both as a working reservoir landscape and a major public destination for camping, boating, fishing, and hiking.