Captain Mullan and his crew celebrated the 4th of July 1861 on top of this mountain as they took a break from clearing passage for the road they were building over it. Thus the current name of "4th of July pass" today.
The Mullan Road was the first wagon road to cross the Rocky Mountains to the Inland of the Pacific Northwest. It was built by U.S. Army Captain John Mullan between the spring of 1859 and summer 1862. It led from Fort Benton, Montana, to Fort Walla Walla, Washington Territory, and it roughly follows the path of modern-day Interstate-90 through the Rockies.
Mullan Road was designated a historic site by the National Register of Historical Places in 1975, and the American Society of Civil Engineers designated it a historic civil engineering landmark in 1977.[2]