On June 29, 1936, President Franklin D. Roosevelt signed legislation (Public Law 840, H.R. 7736) that established Whitman Mission at Waiilatpu as a unit of the National Park Service (NPS). The act stated the following:
On May 31, 1962, the name of the park was changed to Whitman Mission National Historic Site. The change in designation from a monument to a national historic site emphasized its historic significance and the need to address the entire historic setting as well as the existing memorials to the Whitmans.
In 1981, Whitman Mission was officially recognized as a historic site along the Oregon Trail.
(Information excerpted from Whitman Mission NHS General Management Plan, 2000)