Harold J. Cook, son of James H. Cook, built this homestead cabin in the early 1900s and called it East Agate, or "the lower ranch." Fearful that the Carnegie Museum was about to claim the land, he established his homestead to secure ownership rights for the Cook family. From 1910 to 1923, the cabin served as the base camp for numerous research teams conducting fossil digs on the ranch, where Harold worked with many of the world's leading paleontologists at his "bone cabin." The Miocene Epoch fossil discoveries at Agate Springs Ranch were unmatched in the world, and excavations there were conducted by the University of Nebraska, the Carnegie Museum, Amherst College, the American Museum of Natural History, and others. Albert "Bill" Thomson, a field paleontologist for the American Museum from 1911 to 1923, formed a professional relationship with Harold Cook that became a forty year family friendship.