In which year American Civil War was started and why?

Answer 1

War begin on April 12, 1861 and ended in Spring, 1865 with the surrender of Robert E. Lee (the last major Confederate army) to Ulysses S. Grant at Appomattox Courthouse on April 9, 1865.

Reason of the WAR
Slavery abolition by the USA for which south states opposed and revolted.
Two side were called Confederate (opposing the slavery abolition) and Union (supporting slavery abolition)

Answer 2

It was to free the black people from slavery