When id the Civil War end?

There was no peace treaty, for the same reason there had never been an official declaration of war - because Congress had never recognised the Confederacy as a sovereign nation.

The armistice at Appomattox (April 9th 1865) is generally reckoned as the end of the war. Another landmark was the winding-up of the Confederacy at its last cabinet meeting on May 10th 1865. But there was still fighting for a few weeks after that.