The document summarizes several decisive battles of the American Civil War that turned the tide in favor of the Union. The Battle of Gettysburg in 1863 was a major turning point, resulting in heavy casualties on both sides and leading to Lee's retreat. Along with Union victories at Vicksburg and Port Hudson in July 1863, this established the Union's momentum. Later in the war, General Sherman's March to the Sea and capture of Atlanta in 1864 boosted the North. Finally, Grant's siege of Petersburg and Lee's surrender at Appomattox Court House in April 1865 brought the war to an end.