Sweet Home is on the Santiam River in the foothills of the Cascades. Two power generating and flood control reservoirs are on the Santiam River east of the city, Foster and Green Peter Reservoirs. Foster Reservoir is partially within the Sweet Home City Limits.
US Highway 20 runs from Newport Oregon, through Sweet Home along side the Santiam River, crossing the Cascades over Santiam Pass, and then across the United States to Boston, Massachusetts.
Sweet Home is on the east side of the Willamette Valley which lies between the Oregon Coast Range and the Cascade Mountains. The Willamette Valley sweeps from Eugene to Portland. Directly east of Sweet Home in the Cascade Range, within the Willamette National Forest, are currently inactive volcanoes Mt. Jefferson and Mt. Washington. Two grand wilderness areas surround these mountains.
The Cascade Range runs south from Mt. Baker near the Canadian border in northern Washington to Mt. Lassen in northern California. The Cascades feature several prominent volcanic mountains such as Mt. Rainier, east of Seattle, Mt. Hood, east of Portland, and Mt. St. Helens, north of Portland.