 He served the Dodge-Leavenworth Expedition of 1834 and, during the Mexican–American War (1846–1848), led a unit of Indian volunteers as a captain in the U.S. Army.When Captain Randolph B. Marcy escorted the first 500 emigrants from Fort Smith, Arkansas to Santa Fe during the gold rush days of 1849, he engaged Black Beaver as his guide.On his return, Black Beaver took a shortcut across the prairie that reduced the two-month trip to two weeks.