Book excerpt: As the population of the 13 colonies grew and the economy developed, the desire to expand into new land increased. Nineteenth-century Americans believed it was their divine right to expand their territory from the Atlantic Ocean to the Pacific. "Manifest destiny," a phrase first used in 1839 by journalist John O'Sullivan, embodied the belief that God had given the people of the United States a mission to spread a republican democracy across the continent. Advocates of manifest destiny were determined to carry out their mission and instigated several wars, including the war with Mexico to win much of what is now the southwestern United States. In Manifest Destiny: Westward Expansion, learn how this philosophy to spread out across the land shaped our nation.