Tensions between the northern and southern US over the expansion of slavery into new territories increased during the century after independence. With the election of Abraham Lincoln as president in 1861, southern states seceded from the US. Lincoln sought to maintain federal property in the south, leading to the first hostilities, at Fort Sumter. The war, which ended in 1865, claimed more than 600,000 lives. It led to the emancipation of black slaves, and the restoration of the Union.