War of the RebellionA compilation of the official records of the Union and Confederate Armies. Free or open source. Cornell.
Site includes correspondence, orders, reports, and returns of both the Union and Confederate armies. Series I: Formal reports, both Union and Confederate, of the first seizures of United States property in the Southern States, and of all military operations in the field. Series II: Correspondence, orders, reports, and returns, Union and Confederate, relating to prisoners of war. Series III: Correspondence, orders, reports, and returns of the Union authorities. Series IV: Correspondence, orders, reports, and returns of the Confederate authorities.