In the 1890s, Minnesota state geologist Newton H. Winchell and Ulysses S. Grant II surveyed this area and concluded that a peak in the Misquah Hills was the state's highest point, setting its elevation at 2,230 feet with an aneroid barometer. Later observers argued that Eagle Mountain, which Winchell and Grant did not measure and which is visible from the Misquah Hills, was higher. In 1961, a United States Department of the Interior survey team remeasured the area using aerial photographs and controlled bench marks and found Eagle Mountain's elevation to be 2,301 feet, making it Minnesota's highest point. They also determined that the first Misquah Hills peak is exceeded by another unnamed summit, 2,266 feet above sea level, in section 19 of T63N, RIW, in the same western Cook County area. Minnesota's lowest point is Lake Superior at 602 feet, and the igneous rock that composes Eagle Mountain is as old as the Duluth Gabbro, estimated by geologists to be more than a billion years old.