This collection features photographs from the bulletin “Yellow Ore, Yellow Hair, Yellow Pine: A Photographic Study of a Century of Forest Ecology,” published by the Agricultural Experiment Station at South Dakota State University in 1974. The bulletin documents photographic sites from the Custer Black Hills Expedition of 1874. By comparing historical and contemporary scenes, it highlights the changes in vegetation and human impact over the past century. A companion publication, "Following Custer," was released to identify additional 1874 photo sites that were not included in the original study.

William H. Illingworth, hired by the U.S. Army, photographed the Black Hills Expedition in 1874. Though he did not document the exact number of photographs he took, it is believed he produced around 79 glass-plate negatives. Most of these negatives are preserved at the South Dakota State Archives in Pierre, with a few held at the National Archives and the Minnesota Historical Society.

In 1974, Donald R. Progulske, then head of the Department of Wildlife and Fisheries Sciences at South Dakota State University, led the research and fieldwork for these publications. Richard H. Sowell, a photographic technician at the university's Audio-Visual Photo Lab, took the 1974 comparison photographs. Yellow Ore, Yellow Hair, Yellow Pine serves as a study of humanity's impact on the Black Hills environment. This decade-long project documented the expedition's route, spanning 1,205 miles through North Dakota, Wyoming, and South Dakota.

Sowell and Progulske spent three summers retracing the original photographic sites in the Black Hills. By carefully analyzing the details in Illingworth's glass plates, they located the original sites and took contemporary comparison photos.

One significant insight from Progulske’s research is that while human impacts are enduring, conservation efforts have sometimes gone too far, preventing natural processes like forest fires that thin tree populations. He observed that the Black Hills forest has become “closed,” hindering the growth of new plants and trees. Consequently, some photos could not be accurately replicated due to increased tree density at the original locations.