Materials include a four-page letter written from Helena, Montana, by Philip M. Crapo to his sister relating his visit to Yellowstone National Park just months after the area was officially made a national park. Crapo was one of the approximately 300 persons who visited the park in its first year. He describes many of the thermal features, falls of the Yellowstone River, Yellowstone River canyon, and other scenery of the park that he saw in his visit. Dated September 20, 1872.

Collection relates primarily to George D. Marler's research on geysers and hot springs in Yellowstone Park, and related themes. Includes an unpublished autobiography; field notebooks; correspondence; articles and books, including drafts by Marler and others; photographs; slides of thermal features in Yellowstone Park; and other items. Dated 1932 to 1977.