When William Clark passed through this area on July 27, 1806, he described "estonishingly noumerous" bison and elk as well as his last glimpse of the snow-clad Big Horn Mountains. Most importantly, his report of abundant beaver "sign" quickly drew fur trappers and traders to the area, who established several trading posts near the river. They maintained a vigorous trade with the Crow Indians, bartering beaver pelts and bison hides for vital trade goods. By the 1870's steamboats sporadically plied the waters of the Yellowstone carrying supplies to the posts and, in 1876, the FAR WEST carried wounded survivors of the Battle of the Little Bighorn downriver. The Northern Pacific Railway completed its line through here in 1882. In 1912, regional Good Roads enthusiasts and county officials created one of the first interstate highways in the United States, the Yellowstone Trail. It was an interconnected network of county roads blazed by distinctive chrome yellow signs with black arrows. The 4,000 mile highway connected Plymouth Rock, Mass. and Seattle, Wash. with a branch to Yellowstone National Park. The route was re-designated U.S, Highway 10 in 1926.