WASHINGTON — Civil War buffs are getting access to a trove of information: thousands of original maps and diagrams of battles and campaigns between 1861 and 1865, all posted on the Internet.

The Library of Congress is posting 2,240 maps and charts and 76 atlases and sketchbooks, while the Virginia Historical Society and the Library of Virginia are adding about 600 items. Much of the collection is online now at memory.loc.gov/ammem/collections/civil_war_maps; the rest will be posted by spring.

The documents depict troop positions and movements, as well as fortifications. There also are reconnaissance maps, sketches and coastal charts and theater-of-war maps.

One plan of the Mississippi port of Vicksburg was done in 1863, the year Union Gen. Ulysses S. Grant forced its surrender on July 4 in one of the war's most decisive operations. The map includes fortifications, railways, levees, drainage, vegetation and even the names of a few residents.

The same day Vicksburg fell, more than 900 miles away Confederate Gen. Robert E. Lee began retreating to Virginia from Gettysburg, Pa., after his defeat there.

The National Archives and Records Administration recently drew attention to a map of the Gettysburg campaign in its collection that records positions of troops July 2, 1863, when the South came close to winning the battle.

The agency has been looking at the back of some of its documents since it worked with Walt Disney Pictures on the film "National Treasure," a fictional story about a map to hidden treasure on the back of the original Declaration of Independence.

The Gettysburg map, which is not online, went with Lee's report on the battle to Confederate President Jefferson Davis. On the back of Lee's 14-page report was written: "Read with satisfaction and returned to War Dept. Jeffer Davis Aug. 6. 1863."

Davis may have been relieved by the failure of Union Gen. George Meade to pursue and destroy Lee's retreating forces.

The contribution of the Virginia Historical Society includes Confederate maps of Virginia locations. They detail roads, bridges, waterways and buildings, including farms and plantations with the owners' names.

The Virginia society also presents the viewpoint of the Union side, in a diary and scrapbook that belonged to Robert Sneden, an Army mapmaker.

It includes battle plans and fortifications. The society acquired it recently after it had been locked in a bank vault for decades.

The Library of Virginia has maps that went with reports to the governor and field maps of the southwestern part of the state, found in books that belonged to Confederate Gen. William Loring.