【多选题】Which of the statements correctly describe the American Civil War?
A.
The American Civil War was the costliest and deadliest war ever fought on American soil.
B.
The main underlying causes of the American Civil War include simmering tensions between northern and southern states over slavery, states' rights and westward expansion.
C.
The election of Abraham Lincoln in 1860 is the most significant cause of the American Civil War.
D.
The supreme command of the Union armies, Ulysses S. Grant, led the armies to further pursue the Confederates along the Appomattox River, finally exhausting their possibilities for escape.