McNary Dam is a 1.4 mile (2.2 km) long hydroelectric dam which spans the Columbia River. It joins Umatilla County, Oregon with Benton County, Washington, 292 miles (470 km) upriver from the mouth of the Columbia at Astoria, Oregon. It is operated by the U.S. Army Corps of Engineers' McNary Lock and Dam office. The dam is located a mile (2 km) east of the town of Umatilla, Oregon, and 8 miles (13 km) north of Hermiston, Oregon. The dam was originally planned to be named Umatilla Dam, but the Flood Control Act of 1945 renamed the dam in honor of Senator Charles L. McNary of Oregon, who had died the previous year. (Original source - Wikipedia.com)
Hat Rock State Park, located off U.S. Highway 730 nine miles east of Umatilla, lies on the south shore of Lake Wallula behind McNary Dam on the Columbia River. Hat Rock was the first distinctive landmark passed by the Lewis and Clark Expedition on their journey down the Columbia, and is one of the few remaining sites not underwater.