In the late 18th century, the US population was only 4 million but expanded westward due to perceptions of manifest destiny and demand for inexpensive land. Slavery became more controversial as it fueled the southern economy and political battles until the Civil War began in 1860 as southern states seceded to form the Confederate States of America to preserve slavery. The Union defeated the Confederacy in 1865, abolishing slavery and extending rights to freed slaves, but white southern Democrats later imposed Jim Crow laws to maintain white supremacy and prevent African Americans from participating in public life.