The 1st Ohio Artillery Battery I was also known as Dilger’s Battery (Capt. Hubert Dilger (1836-1911). The regiment was organized as early as 1860 under Ohio's militia laws, under Colonel James Barnett. The battery was organized in Cincinnati, Ohio and mustered in for a three year enlistment on December 3, 1861 under Captain Hubert Dilger (1836-1911). During the battle of Gettysburg, the unit served as a member of Osborn’s Brigade in the Eleventh Corps, Army of the Potomac and was still under the command of Dilger. Dilger claimed his pre-war occupation was that of a German artillery officer. Dilger was awarded the Medal of Honor for actions at Chancellorsville. Under Dilger's command, Battery I brought 137 men (and 6 Napoleons) to Gettysburg and among them 13 men were wounded. All totaled by the end of the war, the battery lost a total of 29 men during service; 1 officer and 13 enlisted men killed or mortally wounded, 15 enlisted men died of disease. Battery I, 1st Ohio Light Artillery mustered out of service on June 13, 1865.
The flank monuments are both located on Howard Avenue and are 945 feet apart. The right flank marker is located at N 39° 50.587 W 77° 13.857. Based on the direction and position of the flank monuments, the soldiers were facing north to northeast. The left flank marker is across the road from the primary monument. The right flank monument is about 900 feet (as the crow flies) form the Biglerville Road intersection. The right flank marker is located at the southeast corner of that intersection. Both markers are on the right or the south side of the road if traveling east along Howard Avenue. 
Parking is available along Hancock Avenue at enlarged shoulder cutouts on the side of the road, directly across from the other various monuments. The best parking is on Humphreys Avenue at a dedicated parking lot across from the Pennsylvania Monument. Be sure to keep vehicles off the grass or you will be ticketed by park police. I visited both flank monuments on Thursday, July 5, 2012 @ 10:34 PM, EDT. I was at an elevation of 575 feet, ASL. I used a Canon PowerShot 14.1 Megapixel, SX210 IS digital camera for the photos.
The monuments were dedicated on September 14, 1888 by the State of Ohio. Both granite, flank markers denote the left and right of the section during the July 1st battle along Howard Avenue. Flanking markers are 1.4×1.3 foot. and positioned close to the road. The inscriptions are on the front face, in block, capitalized letters and on a dark gray field while the rest of the monument is light gray, the same color as the incised letters. The half moon symbol of the 11th corps is on top of both monuments. The position markers are referenced and described a few times in the NRHP narrative for the primary monument. The parts concerning these monuments have red font to make it easier to find.
The inscription on the front face of the markers reads as follows:
Left/Right
Battery I
1st. O.L.A.
4 Guns Were Posted
3 Yds. IN Rear Of
This Tablet
While the markers do not qualify for individual contributing status, this monument, along with one other position markers and two flank markers do assist with the primary monument in its contributing status. This position markers and the Battery I, 1st Ohio Artillery Monument collectively are contributing features 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 monument is identified as structure number MN056-F.
From the Nomination Form:
1 of 20 Mn to Ohio. Dilger's 1st Ohio, Battery I Mn indicates pos. of battery July 1, 1863pm. LF&RF indicate pos. of 4 guns & 2 guns, respectively. 4 cannon complete Mn scene. Located W. Howard Avenue. Position marker on E Howard Ave.
Short Physical Description:
Mn, 2 Flank markers, 1 pos. marker, 4 brnz Napoleon cannons mounted on cast-iron carriages. Base: rough-cut 5'3" sq w/ excised polished inscription. Shaft: polished excised inscription & incised inscription; top: detailed cap of fluted caninister & cannon balls. All 13'2"H. RF&LF: 1'4"x1'3"x1'5".
Long Physical Description
Monument that has two flanking markers, one position marker, and four bronze Napoleon cannons. Monument is a granite shaft with a polished excised inscription and incised inscription. The top has detailed cap of fluted canister and cannon balls. Base is 5.3 foot square of rough-cut stone with an excised polished inscription. Overall height is 13.2 foot. Flanking markers are 1.4x1.3 foot. Four cannon mounted on cast iron carriages complete the monument grouping. Located on West Howard Avenue. The position marker is on East Howard Avenue.
My Sources
1.
NRHP Narrative
2.
SIRIS
3.
Stone Sentinels
4.
Virtual Gettysburg
5.
Draw the Sword
6.
Historical Marker Database