At the same time as the initial gold discoveries were being made, the US Army sent lieutenant Frederick Schwatka to reconnoiter the Yukon River. Going over the Chilkoot Pass, his party built rafts and floated down the Yukon River to its mouth in the Bering Sea, naming many geographic features along the way. Schwatka's expedition alarmed the Canadian government, who then sent an expedition under George Mercer Dawson in 1887. William Ogilvie, a surveyor who was later to become famous during the Klondike gold Rush and was part of Dawson's expedition, surveyed the boundary with Alaska.