Impregnable? A detail from a map recently popular with Civil War enthusiasts. Cartographer Charles Reeves combined Orlando Poe’s exacting diagrams from 1863-64 with a modern map of city streets. In bold lines, the map shows the ring of forts that made invasion a discouraging prospect. Forts Higley, Dickerson, and Stanley, with their respective trenchwork, are indicated in the lower half.