This document lists 20 significant battles of the American Civil War between 1861-1864. It provides the date, location, outcome, and brief significance of each battle. Some of the most important battles that turned the tide in favor of the Union include Fort Donelson (1862), Antietam (1862), Gettysburg (1863), Chattanooga (1863), Atlanta (1864), and Nashville (1864). The Union victories at these battles helped secure key territories and weakened Confederate forces.