The Waldo Hills are a range of hills in the Willamette Valley of Oregon, United States. Encompassing an area of around 50 square miles (130 km2), the hills are located east of Salem. The hills are named after pioneer Daniel Waldo.
The hills stretch out from Mill Creek in a northeasterly direction. These hills were formed by a cuesta of Columbia River Basalt Group. Rocks of the hills include Tertiary volcanic bedrock, sedimentary bedrock, and Plio-Pleistocene sedimentary basin fill shaped by elongate domical folds. The Waldo Hills form part of the divider between the upper and lower Willamette Valley. Additionally, the Waldo Hills as part of a larger fault system of low-lying hills in the mid-valley, are the largest geological structure in the mid-Willamette Valley. Along with the Silverton Hills, these hills form the foothills to the Cascade Mountains to the east.
Euro-American settlement of the Waldo Hills began in 1843 when Daniel Waldo settled a land claim there and began farming. Later settlers included Homer Davenport and Samuel L. Simpson, along with Waldo's sons John and William. In 1846, the hills were the site of the formation and drilling of the Oregon Rangers, a militia formed by the Provisional Government of Oregon.
- Corning, Howard M. Dictionary of Oregon History. Binfords & Mort Publishing, 1956.
- Yeats, Robert. Tectonic Setting of the Willamette Valley. Geological Society of America, Accessed September 10, 2007.
- Terry L. Tolan and Marvin H. Beeson. Geologic Map of the Scotts Mills, Silverton, and Stayton Northeast 7.5 Minute Quadrangles, Oregon. Archived 2013-02-17 at the Wayback Machine United States Geological Survey, 1999.
- Brown, J. Henry (1892). Political History of Oregon: Provisional Government. The Lewis & Dryden Printing Co.: Portland.
- Winter scene in the Waldo Hills from Salem Public Library Historic Photographs Collection
- Geologic map of the area
- The Battle of the Abiqua