Union regiments were military units that fought for the Union during the American Civil War from 1861 to 1865. These regiments were typically composed of infantry, cavalry, or artillery and were organized by state. Each regiment usually consisted of around 1,000 soldiers and was identified by a unique number and state designation, such as the 54th Massachusetts or the 1st New York. Union regiments played a crucial role in various battles throughout the war, including the Battle of Gettysburg and the Siege of Vicksburg. They were instrumental in the Union's efforts to preserve the nation and abolish slavery, contributing to the eventual victory over the Confederacy.