Hat Rock State Park near Hermiston, Oregon, preserves a striking Columbia River landmark and a notable piece of western history. Its namesake is a seventy-foot basalt outcrop, with nearby Boat Rock, left exposed after Ice Age floods stripped away softer material from an ancient lava flow landscape about twelve million years old. Hat Rock was the first landmark the Lewis and Clark Expedition passed after reaching the Columbia River, and William Clark’s October 19, 1805, journal description gave it its lasting name. Developed during the McNary Dam era, the park now combines recreation with geologic and historic significance.