McKinney Falls State Park, at the junction of Onion and Williamson creeks on Austin’s southeastern edge, preserves both natural and human history. Its limestone landscape was formed when this region lay beneath an ancient sea, and the falls were carved over millions of years as Onion Creek cut through limestone and volcanic material from the extinct Pilot Knob volcano. People used the area at least 8,750 years ago, and Spanish colonial travelers later passed along El Camino Real de los Tejas. In the 19th century Thomas F. McKinney developed a homestead and gristmill here. Opened as a state park in 1976, it also contains significant archaeological and historic remains.