Fort Yamhill, Military fort and archaeological site in Willamina, United States.

Fort Yamhill is a former U.S. Army post in the Willamina area of Polk County, Oregon, built in 1856 and active until 1866. Its grounds hold the excavated foundations of barracks, officers' quarters, a hospital, a blacksmith shop and a sutler's store; the only standing building is a relocated Officer's Quarters. The wooden blockhouse was moved to a park in downtown Dayton in 1911.

The fort was established in 1856 as a control point for the eastern boundary of the reservation. It managed relations between settlers and Native American communities until it was abandoned in 1866.

Fort Yamhill stood beside the Grand Ronde Agency Coastal Reservation, where members of many western Oregon tribes were resettled in the 1850s. The army post kept a military presence next to that agency rather than serving as a gathering place. The Confederated Tribes of the Grand Ronde now co-manage the Fort Yamhill State Heritage Area with Oregon State Parks and Polk County.

The site functions as a heritage area with walking trails, markers showing former building locations, and informational signs about military operations. Visitors should expect uneven ground and take time to explore the trails to see the different structure sites.

Excavations uncovered intact foundations, a kitchen fireplace, a bakery oven, and numerous artifacts from the military period. These discoveries provide rare insight into daily life for the garrison and how soldiers actually lived on the grounds.