Who won the battle union or confederate how do you know who won?

The Union won the Civil War, which ended in 1865. This is evidenced by the surrender of Confederate General Robert E. Lee at Appomattox Court House, the subsequent surrender of other Confederate forces, and the ratification of the 13th Amendment, which abolished slavery. The Union's victory preserved the United States as one nation and led to significant social and political changes in the nation.