Early explorers on the Columbia River estimated the elevation to be . Two people in Thomas J. Dryer's 1854 expedition calculated the elevation to be and that the tree line was at about . Two months later, a Mr. Belden claimed to have climbed the mountain during a hunting trip and determined it to be upon which "pores oozed blood, eyes bled, and blood rushed from their ears." Sometime by 1866, Reverend G. H. Atkinson determined it to be . A Portland engineer used surveying methods from a Portland baseline and calculated a height of between . Many maps distributed in the late 19th century cited , though Mitchell's School Atlas gave as the correct value. For some time, many references assumed Mount Hood to be the highest point in North America.