1874 On July 17, 1874, the Black Hills Expedition led by Lieutenant Colonel George Armstrong Custer crossed into Wyoming Territory from Montana. A marker about the expedition is located in Crook County. It states; "On July 20, 1874, General George A. Custer, leading the first official government exploring expedition in the Black Hills, crossed at this point en route to the Black Hills to investigate rumors of gold in paying quantities. The trail in the foreground was left by his party which consisted of 110 wagons, 2,000 animals and 1,000 men, including engineers, scouts, geologists and practical miners. This expedition was in violation of the Treaty of 1868, which guaranteed the region to the Indians. In 1875, after government negotiations with the Indians to purchase the Black Hills broke down, miners and settlers poured into this area."