The Army of Northern Virginia was the primary military force of the Confederate States of America in the Eastern Theater of the American Civil War, as well as the primary command structure of the Department of Northern Virginia. It was most often arrayed against the Union Army of the Potomac. The name Army of Northern Virginia referred to its primary area of operation, as did most Confederate States Army names at the time. The Army originated as the (Confederate) Army of the Potomac, which was organized on June 20, 1861, from all operational forces in northern Virginia. On July 20 and July 21, the Army of the Shenandoah and forces from the District of Harpers Ferry were added. Units from the Army of the Northwest were merged into the Army of the Potomac between March 14 and May 17, 1862. The Army of the Potomac was renamed Army of Northern Virginia on March 14. The Army of the Peninsula was merged on April 12, 1862. SOURCE
The Army of Northern Virginia Marker is located on the right or west side of W. Confederate Ave if traveling south, opposite the Virginia Monument. The monument faces the east. Parking is available at small, intermittent cutouts or small shoulders, especially here due to the Virginia monument. Please do not park on the grass, park on the asphalt. I cannot emphasize that enough! You will be ticketed. I visited this monument on Saturday, March 10, 2012 at 2:10 PM, just before the clocks were set ahead for the Spring. I was at a 591 foot ASL elevation.
The monument was built in 1908, according to the NPS/NRHP narrative. The work was done under the direction of the Gettysburg National Park Commission (established by the United States Dept. of War), after they took over the administration of the park from the Gettysburg Battlefield Memorial Association (whose funds had expired) on March 3, 1893, and whose stewardship was then transferred to the Nat'l Park Service in 1933, which entity still operates the park today. SOURCE
Draw the Sword, with descriptive help from the NPS site, offers the following description: A rectangular granite monument, with a large bronze tablets thereon, describing the engagements and movements of the army. Smooth monolith with rough hewn top, 8’9"x4’7" 2’2" wide. Bronze inscription tablet, 3’8"x4’6", mounted on East face. All 8’9" H. The inscription on this tablet reads:
General Robert E. Lee commanding
The Army consisted of Three Army Corps
First Corps Lieutenant General James Longstreet
Second Corps Lieutenant General Richard S. Ewell
Third Corps Lieutenant General Ambrose P. Hill
Cavalry Division Major General J.E.B. Stuart
July 1. Heth's and Pender's Divisions Hill's Corps and Early's and Rodes's Divisions Ewell's Corps reached the field about 1 p.m. and were soon engaged on the North and West of town with the First and Eleventh Corps of the Army of the Potomac. Johnson's Division Ewell's Corps and Anderson's Division Hill's Corps reaching the field about dark were not engaged. Longstreet's Corps on the march.
Stuart's Division marching from Dover to Carlisle.
July 2. McLaws and Hood's Divisions Longstreet's Corps arrived on the field about 3 p.m. and formed facing the Union left. An assault was made by the two Divisions assisted by Anderson's Division Hill's Corps. The Union troops were dislodged from Emmitsburg Road and Peach Orchard engagement lasting until night. Losses heavy. Pickett's Division Longstreet's Corps on the march. Johnson's Division Ewell's Corps about dusk advanced to the assault of Culp's Hill in connection with Early's Divison Ewell's Corps. Rodes's Division Ewell's Corps held position in the valley West of town. Not engaged Heth's and Pender's Divisions Hill's Corps. Stuart's Cavalry on left flank of Confederate Army.
July 3. Pickett's Division Longstreet's Corps reached the field in the mornign. Assaulted the Union line on Cemetery Hill about 3 p.m. assisted by Hill's Corps. The assault failed with great loss. An attack made on the left by Johnson's Division Ewell's Corps reinforced by three Brigades of the Corps failed. Stuart's Cavalry Division engaged with 2d Union Cavalry Division and 2d Brigade 3d Cavalry Division on the Confederate left about 1 p.m.
July 4. The Army took up the line of march during the night.
There are hundreds of non-sculpted monumentation for the various Confederate States & Union units which fought at Gettysburg. There are about 10 different variations of tablets, markers & monoliths by my reckoning. Six designs represent brigade (2), division (2), corps (2), & army headquarters (2), each different in a subtle way so as to distinguish between armies. Battalion/battery/advance position markers & regimental monuments for U.S. Regulars & Confederate have their own distinct design (2), bringing the total to 10 designs at the battlefield. The bronze tablets were created by Albert Russell & Sons Co. of Newburyport, Mass. The granite bases which accompany the various tablets were created by the Van Amringe Company from Boston, Mass. The cast iron tablets were of course manufactured by the aforementioned Calvin Gilbert. The 1910 Gettysburg Commission report lists the awarded contracts to these companies (not Gilbert) for the tablets. All of these tablets were designed by architect Colonel Emmor Bradley Cope (July 23, 1834 - May 28, 1927). He designed pretty much every tablet for both the Union & Rebel armies, each one distinct, w/ several different varieties. He is buried in Evergreen Cemetery 
in Gettysburg, as well he should be as this park and most of the things seen here today were designed by him and as such, are his legacy. These monuments were erected just after the turn of the century during the first & beginning of the second decade of the 20th century. Each one has since been preserved or restored at least twice since the turn of the 21st century. The plaques & tablets were erected by the Gettysburg Park Commission (established by the War Dept.). The Gettysburg Park Commission is also referred to as the Gettysburg National Military Park Commission or the Gettysburg National Park Commission, to clear up any confusions, especially my own.
On October 1, 1898, the Gettysburg National Park Commission in a letter to the Secretary of War set gave recommendations for continuing the task of organizing & progressing the work of the Gettysburg National Military Park. Every November they wrote their annual report which outlined the work of the GNPC for that year. The following is an excerpt from that report relevant to this waymark. The link at the end of the paragraph will take you to the entire report. The method of marking the positions of troops on this field, as approved by the War Department, is to place the principal tablet or monument of each command at the position occupied by the command in the main line of battle, and to mark the several important positions subsequently reached by each command in the course of the battle by subordinate and ancillary tablets, with appropriate brief inscriptions giving interesting details and occurrences and noting the day and hour as nearly as possible. SOURCE
Most of the Commission reports have been digitized and can be found HERE. The initial 1893 report up to & including 1921 can be found here. 1922 to 1926 are missing & have yet to be discovered. The years 1927 to 1933 were discovered in 1996 and are also included. To my knowledge this is the most comprehensive list of documents that illustrated the development and formation of the park.
About these monument types:
CORPS HEADQUARTERS MARKERS (FOR UNION & CONFEDERATE TABLETS)
The two army headquarters markers are unique on the field. Although they share the curved-and-scrolled brass tablet top with corps markers, their stones are much taller and have a curved top. Both Union and Confederate headquarters have a shield attached separately above the tablet, although they do not always stay attached. This monument is missing its badge at the top. SOURCE
The Army of Northern Virginia Marker is a contributing feature to the Gettysburg National Military Park Historic District which is nationally significant under NR Criteria A, B, C & D. Areas of Significance: Military, Politics/Government, Landscape Architecture, Conservation, Archeology-Historic. Period of Significance: 1863-1938. The original National Register Nomination was approved by the Keeper March 19, 1975. An update to this nomination was approved by the Keeper on January 23, 2004. The statue is referenced in the NRHP document as structure number MN793.
From the Nomination Form:
Civil War Marker commemorates "headquarters" area of Army of Northern Virginia during Battle of Gettysburg, 1863. Located opposite site where Lee witnessed the repulse of grand assult on July 3, 1863 & opp VA monument. Adjacent W Confederate Ave adjacent to Spangler Woods.
Short Physical Description:
Smooth monolith w/ rough hewn top, 8'9"x4'7", 2'2" wide. Bronze inscription tablet, 3'8"x4'6", mounted on E face. All 8'9" H.
Long Physical Description:
N/A
My Sources
1.
NRHP Nomination Form
2.
Stone Sentinels
3.
Virtual Gettysburg
4.
Draw the Sword
5.
Historical Marker Database