Caldwell’s Division served as a member of the Second Corps in the Army of the Potomac. The division was commanded by Brigadier General John Curtis Caldwell (April 17, 1833 – August 31, 1912), a teacher, a Union general in the American Civil War, and an American diplomat. At the beginning of the Civil War, Caldwell was 28 years old and had no military experience. Caldwell's bloodiest combat experience was at the Battle of Gettysburg on July 2, 1863. After the war, Caldwell served in the honor guard for Abraham Lincoln's funeral train. He received a brevet promotion to major general on August 19, 1865, and he was mustered out of the volunteer service on January 15, 1866. He returned to civilian life as a lawyer and a member of the Maine Legislature, Caldwell died in Calais, Maine, and is buried at St. Stephen Rural Cemetery in St. Stephen, New Brunswick, Canada.
The Caldwell's Division - US Division Tablet, also known as the Army of The Potomac, 2nd Corps, 1st Division Tablet,is located along South Hancock Avenue on the right or east side if traveling north; the monument faces the west, in the direction of the once approaching Confederate fire. The marker is just before the site where Hancock forks and forms the triangle in the center of which is the Pennsylvania State Monument. 
For parking stay to the left, make another left on Pleasanton Avenue and a left again on Humphreys Avenue (This completes the triangle) and you will see a small lot for 8 cars on the left. There is also a restroom and a broken water fountain. This part of the road is one way and you cannot get to it if traveling north, which is why it is necessary to take the circuitous route. Parking is also available everywhere else along Hancock Avenue, on both sides of the road. This area represents the best of what Gettysburg has to offer, both historically and monumentally and is a beehive of activity. Expect to stay well over an hour for this part of the battlefield. I stayed for four hours. Be sure to keep vehicles off the grass or you will be ticketed by park police. I visited this monument on Thursday, July 5, 2012 late in the afternoon. I used a 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 feet 2 inches x 2 feet x 7 feet in height, consisting of Winnsboro, South Carolina granite. Bronze inscription tablet, 3 feet 8 inches x 3 feet 6¾ inches, is affixed to the polished face of the monolith. Corps insignia, a bronze Maltese Cross, is excised & polished at top of tablet. One of 22 Union division monuments that describe the movements and itinerary of each division of the Army of the Potomac. Designed by E. B. Cope. The trefoil symbol of the Second Corps appears at the top of the tablet, just above the main inscription, on a separate piece of metal. The inscription on this tablet reads:
Army of the Potomac
Second Corps
First Division
Brig. General John C. CaldwellFirst Brigade Col. Edward E. Cross, Col. H. B. McKeen
Second Brigade Col. Patrick Kelly
Third Brigade Brig. Gen. Samuel K. Zook, Lieut. Col. John Fraser
Fourth Brigade Col. J.R. Brooke
July 2. Arrived about 7 a.m. and went into position on the right of the Third Corps on the line between the Cemetery and Round Top. The Second Division on the right. Between 5 and 6 p.m. went into the Wheatfield subject to the orders of Gen. Sykes in support of third line. The line previously occupied by Third Brigade First Division Third Corps. Was engaged with Anderson's Brigade Hood's Division until sunset with heavy losses including Col. Cross and Gen. Zook killed early in the engagement.
Returned to former position in Second Corps line.
July 3. The Division formed in single line threw up breastworks and remained in position until close of the battle.
Casualties. Killed 18 officers 169 men. Wounded 82 officers 798 men. Captured or missing 6 officers 202 men. Total 1275.
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 cast iron tablets were manufactured by 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.), 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, 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.
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 trefoil), 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 Caldwell's Division - 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. MN429.
From the Nomination Form:
1 of 23 Civil War Division Markers in Park. Records movement & itinerary of 2nd Corps, 1st Division, commanded by Brig. Gen. John Caldwell.
Short Physical Description:
Rough-hewn monolith, 4'2"x2'x7'H. Bronze inscription tablet, 3'8"x3'6-3/4", mounted on finished face of monolith. Polished, excised Trefoil Corps insignia centered above tablet.
Long Physical Description:
Located east side Hancock Ave.
My Sources
1. NRHP Nomination Form
2. Stone Sentinels
3. Virtual Gettysburg
4. Draw the Sword
5. Historical Marker Database
6. Wikipedia