General Randolph B Marcy's 1859 book, "The Prairie Traveler" is considered one of the most important guides that made possible the great Western overland migration of United States settlers in the last half of the 19th century. This later book, "Thirty Years of Army Life" is full of Marcy's keen observations of Indian life, hunting, and living in the unsettled western U.S. He knew a great deal about all of these from his many years in the west and from having led a troops of soldiers across the Rocky Mountains in the dead of winter without any loss of life, despite having run out of food during the last two weeks of the trip. Friend and father-in-law to controversial American Civil War general, George B. McClellan, Marcy served under that commander in the war.