After the 1803 Louisiana Purchase, America’s western border moved further west. The debate over slavery expanded west as well. In 1818, the territory of Missouri applied for statehood as a slave state. Two years later, the northern and southern states struck the Missouri Compromise. Missouri entered the Union as the newest slave state and Maine, as a free state. The Compromise drew a line through the middle of America, further dividing the country into South and North.