The 1st Division of the 5th Corps of the Army of the Potomac was also known as Barnes' Division. During the Battle of Gettysburg, this division was ineffectively commanded by Brigadier General James Barnes (December 28, 1801 – February 12, 1869). Barnes was born in Boston, Massachusetts. He attended the Boston Latin School and graduated from the United States Military Academy in 1829, in the same class as Robert E. Lee. However, at age 28 he was older than most West Point cadets upon completion, and placed fifth out of 46 cadets. He was then commissioned a brevet second lieutenant in the 4th U.S. Artillery, but spent most of his army service as an instructor of tactics and French at the Academy. Barnes resigned his commission on July 31, 1836, to become a railroad civil engineer and by 1839 he was superintendent of the Western Railroad, a job he would hold for 22 years.
At Gettysburg, Barnes is much maligned for his performance and lack of leadership. After suffering a wound to the left, he would never return to the battlefield. Barnes did get personally involved with his other two brigades, who were sent to reinforce the Union line in the Wheatfield, and here his career took a fatal downward turn. He was criticized after the battle for withdrawing his two brigades under Colonels Jacob B. Sweitzer and William S. Tilton 300 yards back from the Wheatfield without permission, despite protests from the generals on his flanks. When reinforcements from the II Corps arrived, Maj. Gen. David B. Birney gave orders for Barnes' men to lie down while the brigade of Brig. Gen. Samuel K. Zook marched over them. Sweitzer's brigade was sent into the Wheatfield, where it was attacked in the flank by another Confederate charge led by Brig. Gen. William T. Wofford. Aides could not find Barnes in the vicinity of his troops. Later that day, Barnes was wounded in the leg and although it healed, he would never return to combat duty.
After the war, Barnes returned to his profession of railroad civil engineering and was a member of the government commission that supervised the building of the Union Pacific Railroad. Barnes died in Springfield, Massachusetts, and is buried there in Springfield Cemetery.
The Barnes' US Division Tablet is located on the right or east side of Sickles Avenue if traveling northeast. The monument is 362 feet south of the T-Intersection with Wheatfield Road. This part of Sickles Avenue is one-way. This is also the first monument after The Loop. Parking is available along the side of the road at intermittently enlarged shoulders. Take care to park in the white lines or on asphalt widened shoulders and not park on anything remotely green looking as Park Police will happily ticket you. I visited this site on Monday, July 1, 2013 on the 150th anniversary of the Battle of Gettysburg after 6:04 PM, EDT & @ an altitude of 565 feet, ASL. As always, I used my trusty and oft abused Canon PowerShot 14.1 Megapixel, SX210 IS digital camera for the photos.
Draw the Sword, with descriptive help from the NPS site, offers the following description: Monuments are rough-hewn monoliths, 4'2" x 2' x 7' in height, consisting of Winnsboro, South Carolina granite. Bronze inscription tablet, 3'8' x 3'6¾", is affixed to the polished face of the monolith. Corps insignia, a bronze Maltese Cross, is excised & polished at top of tablet.
Army of the Potomac
Fifth Corps
First Division
Brig. General James Barnes
First Brigade Col. Wm. S. Tilton
Second Brigade Col. J.B. Sweitzer
Third Brigade Col. Strong Vincent, Col. Jas. C. Rice.
July 2. Crossed Rock Creek in the morning and was massed on Baltimore Pike with the Corps until between 4 and 5 p.m. then moved to the left by command of Gen. Sykes to the support of Third Corps line. The Third Brigade in the advance hastened to take possession of Little Round Top. The First and Second Brigades crossed Plum Run and the Wheatfield to the further edge of the woods beyond near the Rose House. First Brigade was formed on the right of Second. These Brigades were more or less engaged until after sundown when with other troops on the line they were compelled to retire to a line extending north from the summit of Little Round Top.
July 3. The Third Brigade was relieved by the First Brigade and joined Second Brigade north of Little Round Top. Remained in these positions until the close of the battle except reconnoissances to the front.
Casualties. Killed 14 officers 153 men. Wounded 55 officers 539 men. Captured or missing 1 officer 142 men. Total 904.
There are hundreds of non-sculpted monumentation for the various Regular Union (Army of the Potomac - Federals) units & "Regular" Confederate units engaged at Gettysburg from July 1-3, 1863. There are about 10 different variations of tablets, markers & monoliths by my reckoning. Six designs represent brigade (2), division (2), corps (2), & army headquarters (only 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 (these ones, too) 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 1910 Gettysburg Commission report lists the awarded contracts to these companies.
The inscribed tables on the granite monuments were cast by Calvin Gilbert. Gilbert joined the 87th Pennsylvania Volunteers when the "Rebellion" broke out. Since he was musically inclined, he was made a member of the regimental band. In early 1863, he was promoted to the rank of Captain and sent to Washington D.C. for commissary duty. He served in that capacity until the war ended in 1865, and at war’s end earned the brevet rank of Major. 
After returning home to Gettysburg, Major Gilbert moved his family to the town of Chambersburg, where he served as the Superintendent of Schools. He also opened an iron foundry there in 1868. When Calvin learned, nearly thirty years later, in 1894, that the Gettysburg Foundry was available, he purchased it with a business partner & moved his family back to Gettysburg. For the next twenty years, the Calvin Gilbert Foundry created ironworks that are still seen today on many historic forts and national battlefields (this tablet), from upstate New York to Florida to Lookout Mountain. Gilbert lived to be 100 years old and attended the Last Reunion of the Blue and Gray for the 75th anniversary of the Battle of Gettysburg when he was 99. He was a most remarkable man who lived an amazing life.
There is an excellent excerpt in the American Guide Series about Gilbert attending the 75th reunion anniversary.
All of these monoliths were designed by architect Colonel Emmor Bradley Cope (July 23, 1834 - May 28, 1927). He designed pretty much every monument 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. The monuments were erected by the Gettysburg Park Commission (established by the War Dept.), 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 National Park Service in 1933) SOURCE The Gettysburg Park Commission is also referred to as the Gettysburg National Military Park Commission or the Gettysburg National Park Commission.
On October 1, 1898, the Gettysburg National Park Commission in a letter to the Secretary of War 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.
Information about these specific types of monuments:
DIVISION HEADQUARTERS MARKERS (For Union & Confederate Monuments)
Division headquarters are rectangular bronze tablets mounted on large, rectangular stones. Union headquarters have a corps or service branch symbol (like a cross, clover, star or crescent moon) as a separate bronze piece above the tablet (this one has the Maltese cross), while Confederate headquarters are labeled "C.S.A." on a separate bronze piece in an oval. There are 22 Union and 10 Confederate Division markers at Gettysburg. Both markers are of similar design and were all construed of Winnsboro (S.C.), granite. Each stands seven feet in height. SOURCE & SOURCE
The Barnes' US Division Tablet is a contributing feature to the Gettysburg Nat'l Military Park H.D. which is nationally significant under NR Criteria A, B, C & D. Areas of Significance: Military, Politics/Gov't, Landscape Architecture, Conservation, Archeology-Historic. Period of Significance: 1863-1938. The monument is designated as structure no. MN435.
From the Nomination Form:
1 of 23 Civil War US Division Markers in Park indicating the general positions of the various Union divisions during the battle. Records movement & itinerary of 5th Corps, 1st Division under the command of Brig. General James Barnes. Located on Sickles Avenue, north of the Loop.
Short Physical Description:
Rough-hewn monolith, 4'2"x2'x7'H. Bronze inscription tablet, 3'8"x3'6-3/4", mounted on polished face of monolith. High polished, excised Maltese Cross insignia centered above tablet.
Long Physical Description:
Located on E side of Crawford Avenue, S of Wheatfield Avenue.
My Sources
1. NRHP Nomination Form
2. Stone Sentinels
3. Virtual Gettysburg
4. Draw the Sword
5. Historical Marker Database
6. Wikipedia