After the Civil War, the U.S. Government and the Army embarked on a landmark joint endeavor. For the first time in American history, the federal government itself —led by the Army— compiled a military history. The history was composed of all of the official military documents from both sides of the war, and it proved to be a massive production. It was called *War of the Rebellion: A Compilation of the Official Records of the Union and Confederate Armies*, and referred to as the Official Records, or O.R. It contained official reports, letters, telegrams, strength returns, and casualty lists, covering all theaters throughout the war. The Army then got together the official military maps to supplement the O.R. This was called *The Atlas to Accompany the Official Records of the Union and Confederate Armies*. The maps had been drawn during the war by engineers, draftsmen, and sometimes even generals themselves for actual military use. Only a few maps, drawn later by cartographers, were added for historical purposes. Tactical and strategic maps indicate troop dispositions, defense lines, redoubts, and fortification of key sites are clearly shown. Terrain maps often contain picket positions, signal stations, and lines of march. Some are rough sketches, some cartographic masterpieces. All are informative and reveal the knowledge —or lack of knowledge— that both sides possessed about the terrain, and the strength and the position of opposing troops.