The park is located off the east side of U.S. Highway 730 in Hermiston,[2] on the south shore of Lake Wallula behind McNary Dam on the Columbia River.

Floods from the Ice Age eventually left these bedrocks, as well as others along the Columbia River Gorge exposed at the surface of the Earth.

On October 19, 1805, Clark noted in his journal "a rock on the Lard... resembling a hat".

[5][6] During the construction of the nearby McNary Dam in 1951, 175 acres were purchased by Oregon State Parks from Charles and Eileen Kirk for $5,000.

Another 191 acres were leased from the Army Corps of Engineers in 1953, with 2 small additional parcels purchased in the following years.