The Waldo Hills are a broad range in Oregon’s Willamette Valley east of Salem, covering about 50 square miles and forming part of the divide between the upper and lower valley. Created from Columbia River Basalt Group formations, they include volcanic and sedimentary bedrock along with younger basin fill shaped by domical folds, and with the nearby Silverton Hills they rise toward the Cascade foothills. Named for pioneer Daniel Waldo, an early Euro-American settler who began farming there in 1843, the hills also became notable in 1846 as the place where the Oregon Rangers, a militia of the Provisional Government of Oregon, were organized and drilled.