Mill City is located at 832 feet above sea level in the Santiam Canyon and considered part of the foothills of the Cascade Range. Shaped by the North Santiam River, the canyon is a result of seasonal glacier melts from the southern face of Mt. Jefferson to the east and many tributaries scattered along the canyon, the largest being the Breitenbush River which meets the Santiam in Detroit, roughly east of Mill City. The looming canyon walls are the most noticeable feature in passing from Highway 22; however, look more like tall hills on the north and south sides of Mill City. Further into town two bridges allow crossing of the North Santiam River.