Sources for Civil War Maps
Virginia Center for Digital History
War Years Animated Eastern Theater of War Maps – 1861-1865
Ohio State University’s eHistory archive
American Civil War Maps
Speaking of The Battle of the Crater, I found this at the Library of Congress. This is a zoomed in view of pages of what appears to be a journal. Whether intended or not, it implies by its shape a salient (see previous post: Military History Word of the Day – “Salient”). The author appears to be unknown.