Crater of Diamonds State Park near Murfreesboro, Arkansas, preserves one of the world’s few public diamond-bearing sites, where visitors may search a plowed field and keep what they find. Set over an eroded volcanic pipe, the site has yielded diamonds since John Wesley Huddleston discovered them there in 1906, sparking a brief rush and repeated but largely unsuccessful commercial mining efforts. Its lasting importance comes from both public access and notable discoveries, including the Uncle Sam, the largest diamond ever found in the United States. Since becoming a state park in 1972, it has combined active searching with interpretation of the unusual geology that brought diamonds and other minerals to the surface.