Civil War History
A day after defeating Confederate forces in the Battle of Gettysburg in Pennsylvania, Union forces accepted the surrender of Confederate forces in Vicksburg, Mississippi, after a long siege. Vicksburg was the last major Confederate stronghold on the Mississippi River and its loss effectively meant the Confederacy was split in half.
Outside of the formation of our country, there might not be any more significant days in American history than July 3 and 4, 1863. The Confederacy would never be able to recover and the country would stay intact.