The lake was formed by damming the Wisconsin River just downstream of its confluence with the Yellow River. Its surface area of nearly 14,000 acres places Castle Rock as the fifth largest lake in Wisconsin.
The land that remained above water between the two rivers became known locally as the Buckhorn peninsula. A little more than 4,500 acres at the tip of the peninsula and along the Yellow River were purchased by the state and became Buckhorn State Park and Wildlife Area.
The open waters of the flowage are the domain of every type of watercraft imaginable. Bass boats, sailboats, ski boats, pontoon boats, jet skis, and even houseboats can be seen in constant motion. The sloughs and back-waters of the flowage, however, offer a slower, quieter experience to canoeists.
The park offers a developed beach area, boat ramp and fishing pier. Changing stalls, toilets and a play area are found adjacent to the beach.
