American and British disputes in the region centered on the fur trade, and the Treaty of 1818 allowed for joint administration of Oregon Country, as it was referred to in the United Statesthe British Empire referred to the region as the Columbia District. The treaty set the international border at the 49th parallel, but this was disputed west of the Rocky Mountains, since the rival fur trading outfits had their own ideas about where the border should be. The Oregon boundary dispute between Britain and the United States eventually led to the Oregon Treaty of 1846, and the 49th parallel forms both the current international border as well as the northern limit of the current park. During the late 1850s, members of the US North West Boundary Commission explored the border region, attempting to identify which mountains, rivers and lakes belonged to which country. One party of the commission was led by explorer Henry Custer, and they explored the northern district of the park, publishing their report in the 1860s. Custer's party crossed Whatcom Pass in 1858, and were the first whites to see Challenger Glacier and Hozomeen Mountain. Impressed with the scenic grandeur of the region, Custer stated, "must be seen, it cannot be described".