The Union Army regiments were organized units of soldiers that fought for the Northern states during the American Civil War (1861-1865). Each regiment typically consisted of around 1,000 men and was often formed from volunteers from specific states or regions. They were designated by numbers and often had names reflecting their home state, such as the 1st Massachusetts or the 20th Maine. Regiments were further divided into companies, usually consisting of 100 men each. These units played crucial roles in various battles and campaigns, contributing to the overall strategy of the Union forces. The structure allowed for effective command and coordination on the battlefield.