A series of Native American groups inhabited the area from as early as 7000 BC, most recently the Timbisha around 1000 AD who migrated between winter camps in the valleys and summer grounds in the mountains. A group of European Americans, trapped in the valley in 1849 while looking for a shortcut to the gold fields of California, gave the valley its name, even though only one of their group died there. Several short-lived boom towns sprang up during the late 19th and early 20th centuries to mine gold and silver. The only long-term profitable ore to be mined was borax, which was transported out of the valley with twenty-mule teams. The valley later became the subject of books, radio programs, television series, and movies. Tourism expanded in the 1920s when resorts were built around Stovepipe Wells and Furnace Creek. Death Valley National Monument was declared in 1933 and the park was substantially expanded and became a national park in 1994.