The 1862 E.G. Arnold map of the District of Columbia, famously suppressed soon after publication and thus one of the rarest and most sought after Civil War maps of Washington, D.C. and surroundings.
At the start of 1861 Washington, D.C. was a small, dusty city of 60,000, when by contrast the population of New York was approaching 1.2 million. The Civil War changed everything, as Washington swelled with members of the growing Federal bureaucracy; soldiers garrisoning the city, heading south or convalescing from their wounds; and thousands of non-combatants supporting the war effort. The city underwent a construction boom, involving among other things a ring of dozens of forts nearly 40 miles in circumference, most connected by purpose-built military roads.
This remarkable map by Civil Engineer E.G. Arnold documents a city transformed. It encompasses the “Original District of Columbia,” laid out by Andrew Ellicott in 1791-92 as a ten-mile-square diamond straddling the Potomac River (The Virginia portion was retroceded to that state in 1846.) The area’s topography is shown by hachuring, and the network of roads, turnpikes, and railroads is shown in great detail, as are the routes of the Chesapeake & Ohio Canal and the nearly-completed Washington Aqueduct. Of particular interest is the ring of forts indicated by small, red circles and, poignantly, the many hospitals built just north of the city to care for the wounded. At lower left are historical population tables going back to 1800 and a brief geographical description of the city. The whole is adorned by a delicate foliate border, which together with the delicate coloring gives the image considerable decorative appeal.
Unfortunately for Arnold and publisher George W. Colton the map appeared in early September of 1862, within days of the Union disaster at the Second Battle of Bull Run just miles from Washington. Neither man had informed the authorities about the map, and its abundance of information about topography and fortifications rendered it of immense potential value to the Confederacy. The War Department acted quickly and aggressively to suppress the work:
“…two days after the first copy had been put on sale, the rumor of its existence reached the ears of the War Department, and the officers of the law swooped down on the bookstores and gobbled every copy in stock…. Not only were all the bookstore copies taken, but the name [sic] of those who had bought copies of the map were also learned, and those individuals were promptly called upon and given the alternative of surrendering their purchase or of going to the Old Capitol, which was then the political prison of the city. The plate from which the map had been printed was confiscated as well….” (Washington Post, Nov. 6, 1892)
As a result the map is today quite scarce, though it was likely printed in great numbers.
Miller, Washington in Maps, pp. 88-89. Phillips, Maps of America, p. 266. Stephenson, Civil War Maps, #674.
 The first ad I find is in the Philadelphia Inquirer for September 10, 1862.