The State of California created the Donner Memorial State Park in 1927. It originally consisted of 11 acres (4.5 ha) surrounding the monument. Twenty years later, the site of the Murphy cabin was purchased and added to the park. In 1962, the Emigrant Trail Museum was added to tell the history of westward migration into California. The Murphy cabin and Donner monument were established as a National Historic Landmark in 1963. A large rock served as the back-end of the fireplace of the Murphy cabin, and a bronze plaque has been affixed to the rock listing the members of the Donner Party, indicating who survived and who did not. The State of California justifies memorializing the site because the episode was "an isolated and tragic incident of American history that has been transformed into a major folk epic". As of 2003, the park is estimated to receive 200,000 visitors a year.