The Willamette Stone was a small stone obelisk originally installed by the Department of Interior in 1885 in the western hills of Portland, Oregon, in the United States to mark the intersection and origin of the Willamette meridian and Willamette baseline. It replaced a cedar stake placed by the Surveyor General of the Oregon Territory in 1851; this stake defined the grid system of sections and townships from which all real property in the states of Oregon and Washington has been measured following the Donation Land Claim Act of 1850. The Willamette meridian runs north–south, and the Willamette baseline runs east–west through the marker. The easternmost northeast corner of Washington County is sited on the marker.