The following excerpt is from the National Archives blog.
Sept. 21, 2021: Civil War era and related maps from the Army Corps of Engineers have been digitized and are available to view and download from the National Archives Catalog. The records are part of the Civil Works Map File series from Record Group 77, Records of the Office of the Chief of Engineers. The records make up the Z file unit.
The records in the Civil Works Map File comprised the main map collection for the Corps of Engineers during the nineteenth and early-twentieth centuries. They include manuscript maps forwarded to headquarters by Corps of Topographic Engineers and Army Engineer surveyors and cartographers in the field, and published editions of selected maps. The maps pertain to numerous subjects, including surveys of the Mississippi River, Great Lakes, and other bodies of water; construction or improvement of harbors, canals, roads, railroads and other internal improvements; exploration of the West and surveying of western terrain; location of posts and fortifications, Indian tribes, and settlements in western territories; military roads and routes between Army posts; campaigns and battlefields of the Revolutionary War, the Seminole War in Florida, Indian Wars in the West, the Mexican War, and the Civil War (including both Union Army maps and Confederate Army maps acquired by Union forces); surveys of boundaries between States and Territories; and numerous foreign areas. Architectural and engineering drawings in this series relate to canals, bridges, dams, piers, and jetties as built along the coasts and inland waterways. Also included are plans of dredge boats used in improving rivers and harbors.