Stripping Overburden at Fossil Horse Quarry Near Hagerman, Idaho, 1931, Smithsonian Institution Archives, Overburden being stripped from the fossil horse quarry near Hagerman, Idaho. United States National Museum field crews excavated from three quarry beds in the area during 1929-1931 and again in 1934. The three individuals depicted are believed to be C. P. Singleton (holding the horse's reins) and local assistants C. W. Caldwell and Charles Bremer..