Yes, there is a map of the wartime locations and I have it posted in my classroom. I got it from the National Archives. As for an overlay map, I would direct you to the recent book about the Battle of Galveston. Forgive me if I can't be more specific, as I am a high school teacher in Texas and have most of my sources at the school. I will give you the title and author on Monday. The book basically shows only the battle areas in an overlay map form, not the rest of the fortifications. As I am sure you know, Galveston was heavily fortified, so it would be quite a project to do an overlay map of all of the sites.