Federal military authorities were keenly aware that they were unprepared to fight a war on American soil. Any significant campaign into the seceding states could be successfully carried out only after good maps, based on reliable data from the field, had been prepared. Existing Federal mapping units, such as the Army's Corps of Topographical Engineers and Corps of Engineers, the Treasury Department's Coast Survey, and the Navy's Hydrographic Office, therefore, were considered of immense importance to the war effort and were given full support to expand and carry out their missions. Although Federal authorities were unprepared to fight a war, they had one great advantage over the Confederacy: they were able to build upon an existing organizational structure, which included equipment and trained personnel.
Mapping of Washington, D.C.
As the war began, perhaps the most vulnerable area of the Union was the nation's capital. Situated on the banks of the Potomac River, Washington, D.C., was located between the Commonwealth of Virginia which ratified the ordinance of secession on April 17, 1861, and Maryland, which initially wavered, but remained a part of the Union. On the evening of May 23, as soon as sufficient troops were on hand in the nation's capital, Federal regiments crossed the Potomac into Virginia and began occupying the strategic approaches to the city. Within the next two months efforts were concentrated on the preparation of earthen fortifications to defend the city from an attack from the South. Throughout the war the defenses of Washington were extended, strengthened, and modified. Entrusted with this important task was Bvt. Maj. Gen. John G. Barnard of the Corps of Engineers. General Barnard served as Chief Engineer of the Army of the Potomac, 1861 to 1862, Chief Engineer of the Department of Washington from 1861 to 1864, and then as Chief Engineer of the armies in the field from 1864 to 1865. In his Report on the Defenses of Washington published after the war, Barnard noted with some pride that:
From a few isolated works covering bridges or commanding a few especially important points, was developed a connected system of fortification by which every prominent point, at intervals of 800 to 1,000 yards, was occupied by an inclosed field-fort every important approach or depression of ground, unseen from the forts, swept by a battery for field-guns, and the whole connected by rifle-trenches which were in fact lines of infantry parapet, furnishing emplacement for two ranks of men and affording covered communication along the line, while roads were opened wherever necessary, so that troops and artillery could be moved rapidly from one point of the immense periphery to another, or under cover, from point to point along the line.
Of the numerous maps depicting the defenses of Washington, D.C., the detailed map compiled by the U.S. Army Corps of Engineers showing the entire interlinking network of fortifications is of particular importance. Measuring 132 by 144 cm., this remarkable map was made to accompany General Barnard's official report on the defenses of the nation's capital. Albert Boschke's notable 1861 printed map of Washington, D.C., was used as the base, and to it army mapmakers added, by hand, cultural data on Virginia, a new map title, forts, batteries, and rifle pits, as well as the military roads built to link them (LC Civil War Maps no. 676).
Mapping of Northern Virginia
Occupancy of key positions in Virginia enabled Federal officials to begin the first major mapping project of the war. In June 1861, on orders from Winfield Scott, General in Chief of the Army, two field parties made up of U.S. Coast Survey personnel and under the direction of H.L. Whiting, the survey's "most experienced field assistant," began a 38-square-mile plane table survey of the secured part of northern Virginia. Transportation and protection were provided by army detachments, and the actual map itself was compiled in the Topographical Engineers Office at the Division Headquarters of Gen. Irvin McDowell at Arlington, Virginia. This cooperative undertaking involving both Coast Survey and army personnel was to be the pattern followed throughout the war. Coast Survey assistants provided valuable service to armies in the field as well as to the naval squadrons blockading Southern bays, harbors, and ports.
Work on the map was interrupted in July when Federal troops in northern Virginia suffered a jolting defeat at Manassas, Virginia (Bull Run). The need for an accurate map of northern Virginia was reinforced by the Union disaster only a few miles from the capital city. Work was quickly resumed on this key map and, under orders from Gen. George McClellan, who had assumed command of the armies around Washington, the area covered by the survey was significantly expanded. The first edition of the map was "engraved on stone" and issued on January 1, 1862.
A second edition incorporating corrections "from recent surveys and reconnaissances under direction of the Bureau of Topographical Engineers" was published on August 1, 1862, only 28 days before the second Battle of Manassas, Virginia.
Published at the scale of one inch to one mile (1:63,360), field assistant Whiting commented that "The detailed survey shows all the important topographical features of the country which it embraces; the main roads, by-roads, and bridle-paths; the woods, open grounds, and streams; houses, out-buildings, and fences; with as close a sketch of contour as the hidden character of the country would allow--producing in all a map by which any practicable military movement might be studied and planned with perfect reliability." This was the first detailed map of northern Virginia to be compiled and published, and it remains today an essential cartographic tool for the study of that region at mid-nineteenth century (LC Civil War Maps nos. 466-470).
Federal authorities used every means at their disposal to gather accurate information on the location, number, movement, and intent of Confederate armed forces. Army cavalry parties were constantly probing the countryside in search of the enemy's picket lines; travelers and peddlers were interrogated; Southerners sympathetic to the Union were contacted and questioned; and spies were dispatched into the interior to obtain information. The army also turned to a new device for gathering information, the stationary observation balloon. Early in the war a balloon corps under the direction of Thaddeus Lowe was established and attached to the Army of the Potomac. Although used chiefly for observing the enemy's position in the field, the balloon was also successfully employed for the making of maps and sketches. Aeronaut John La Montain made one of the earliest sketches from the platform of a balloon. Dated August 10, 1861, the simple sketch shows the location of Confederate tents and batteries at Sewall's Point, Virginia (LC Civil War Maps no. 654).
The Geography and Map Division has an interesting reconnaissance map prepared during the crucial Seven Days' battles of the Peninsula Campaign. It was compiled under the alias of E.J. Allen, by the famous nineteenth-century detective Allan Pinkerton, with the assistance of one of his operatives, John C. Babcock. Pinkerton, who earlier had established the U.S. Secret Service in Washington, served as McClellan's chief of intelligence during the Peninsula Campaign. Based in part on the prewar map of Henrico County by James Keily, Pinkerton and Babcock's map includes a wealth of up-to-date military information, such as Confederate batteries, Federal lines, and Federal cavalry and infantry pickets. The faded sunprint in the Geography and Map Division was initially prepared on May 31, 1862, corrected on June 20, and again on July 22 (LC Civil War Maps no. 620).
Another badly faded issue of this map is preserved in the Library's Manuscript Division. This photocopy, dated June 6, 1862, is particularly noteworthy because it has been annotated in red and black inks to show information obtained from two tethered balloons (LC Civil War Maps no. 619.5). A note written by Thaddeus Lowe at the bottom of the map reads as follows:
Balloon Camp, June 14th 1862.
The red lines represent some of the most important earth works seen this
morning & are located as near as possible, as is also the camps in black ink.
As soon as I can get an observation from the Mechanicsville Balloon I can make
many additions to this map.
[Signed] T.S.C. Lowe
Field and harbor surveys, topographic and hydrographic surveys, reconnaissance, and road traverses by Federal mappers led to the preparation of countless thousands of manuscript maps and the publication of maps and charts in unprecedented numbers. The Superintendent of the Coast Survey in his annual report for 1862 noted that "upwards of forty-four thousand copies of printed maps, charts, and sketches have been sent from the office since the date of my last report--a number more than double the distribution in the year 1861, and upwards of five times the average annual distribution of former years. This large and increasing issue of charts within the past two years has been due to the constant demands of the Navy and War Departments, every effort to supply which still continues to be made." By 1864, the number of maps and charts printed during the year reached 65,897, of which more than 22,000 were military maps and sketches. Large numbers of maps also were compiled and printed by the Army's Corps of Engineers. The Chief Engineer reported that in 1864, 20,938 map sheets were furnished to the armies in the field, and in the final year of the war this figure grew to 24,591.
The great demand for maps and charts could not have been met were it not for the introduction of two lithographic presses in the Coast Survey office in 1861. Previously, the Survey, like most other Federal mapping agencies, was dependent upon the laborious and time-consuming process of printing maps from engraved copper plates. Because of the ease in transferring manuscript data to stone, the versatility of the process, and the speed of the lithographic presses, reliance on lithography grew rapidly during the war. By 1863, the Superintendent reported that "Two lithographic presses have been kept in constant operation throughout the year, and such has occasionally been the pressure on the division that it has been found necessary to employ other lithographic establishments in the execution of special jobs." To help satisfy the Federal government's printing demands, commercial firms such as Julius Bien and Company in New York, and Bowen and Company in Philadelphia were hired to print the needed maps.
The development and growing sophistication of the Union mapping effort was apparent in 1864 when it became possible for Coast Survey officials to compile a uniform, ten-mile-to-the-inch base map described by the Superintendent as "the area of all the States in rebellion east of the Mississippi river, excepting the back districts of North and South Carolina, and the neutral part of Tennessee and to southern Florida, in which no military movements have taken place." Moreover, as the Superintendent noted, the map was placed on lithographic stones so that "any limits for a special map may be chosen at pleasure, and a sheet issued promptly when needed in prospective military movements." During the final two years of the conflict, numerous regional base maps at ten miles to the inch and showing boundaries, relief, place names and lines of transportation were issued by the Coast Survey. Some were printed without map titles, such as the map of eastern Tennessee and environs (LC Civil War Maps no. 75.8), while others bore map titles, such as the map of "North Carolina & South Carolina" (LC Civil War Maps no. 305a.4).
Throughout the war military publishing authorities continued to favor the use of hachures to depict relief on published maps. Although contour lines or "horizontal curves," as they were sometimes called, were used increasingly by topographic engineers in their field surveys, the technique apparently was not considered satisfactory for the finished or published map. Col. William E. Merrill, for example, submitted to the Engineer Department a topographic survey of the battlefield of Chickamauga, Georgia on which relief is represented by contour lines at 20-foot intervals and layer tints. In an explanatory note, Merrill wrote that "This map was prepared as a guide to the draughtsman who might be employed to prepare the complete map of the battle of Chicamauga [sic]. By carefully studying the contour lines and tints on this map an accurate map with hachures may be made of the ground" (LC Civil War Maps no. 157.4).
The map of the "Approaches to Grand Gulf. From a Topographical & Hydrographical Survey by F.H. Gerdes" is an example of a printed map in which the publisher favored hachures over contours to depict the topography of the area. On file in the Geography and Map Division is a photocopy of a preliminary version of the Grand Gulf map with annotations in ink and pencil (LC Civil War Maps no. 271). Believed to be Gerdes's field copy, it shows that he elected to indicate relief by contour lines rather than by hachures. By the time the map was issued, however, the publisher had converted this information into the more conventional hachure technique with which the nonexpert was more familiar (LC Civil War Maps no. 270).
Richard W. Stephenson, Civil War Maps
Source: Library of Congress