The United States had just increased its size by a full quarter. The War with Mexico cost the United States rather little and brought it rich rewards. In return for a sixteen-month conflict that indicated the prowess of American arms, the United States gained California, New Mexico, Arizona, and much of what is now Utah. The acquisition of these territories seemed like an unmitigated blessing, but it also opened the door to a renewed debate on the merits and demerits of the institution of slavery.