The Waldo Hills are a range of hills in the Willamette Valley of Oregon, United States. Encompassing an area of around 50sqmi, the hills are located east of Salem.[1] The hills are named after pioneer Daniel Waldo.
The hills stretch out from Mill Creek in a northeasterly direction.[1] These hills were formed by a cuesta of Columbia River Basalt Group.[2] Rocks of the hills include Tertiary volcanic bedrock, sedimentary bedrock, and Plio-Pleistocene sedimentary basin fill shaped by elongate domical folds.[3] The Waldo Hills form part of the divider between the upper and lower Willamette Valley.[2] 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.[2] Along with the Silverton Hills, these hills form the foothills to the Cascade Mountains to the east.[3]
Euro-American settlement of the Waldo Hills began in 1843 when Daniel Waldo settled a land claim there and began farming.[1] Later settlers included Homer Davenport and Samuel L. Simpson, along with Waldo's sons John and William.[1] 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.[4]