The 19th Maine Infantry served as a member of Harrow’s Brigade in Gibbon’s Division of the Second Corps, Army of the Potomac, a Fighting 300 Regiment. The unit was commanded by Colonel Francis E. Heath (1838 - 1897). Heath was a clerk from Waterville. He was wounded @ Gettysburg on July 3. In his post-war life he served in the state legislature. Under Heath's command, 543 men were engaged at Gettysburg and among them, 29 were killed, 170 were wounded and 4 went missing.
The 19th Maine Infantry Monument is located on the left or west side of 
Hancock Avenue (RD310) if traveling north along the road at an area called The Angle. This monument is the sixth sculpture in a string of monuments that extend north across the green field to the United States Regulars Monument (MN235), which is a few feet northwest of this position, and beyond. All totaled, there are about 1080 feet of green fields with a line of monumentation spread across it representing the line of union regiments who defended Cemetery Ridge at The Angle against Longstreet's assault also referred to as Pickett's Charge on July 3, 1863, the final day of the Great Battle. The 15th Massachusetts Infantry Monument (MN203-B) is 72 feet south or left (if facing west) of the 19th Maine monument. The 1st Minnesota Infantry Monument (MN239) is the next monument to the south. Next is the 82nd New York Infantry Monument (MN239) and then the 20th New York State Militia (80th Regiment) Marker (MN798). 
Parking is plentiful and is available road-side at intermittently enlarged shoulder cut-outs, usually marked with white striping. Be sure to keep vehicles off the grass or you will be ticketed by park police. I visited this monument on Tuesday, August 7, 2012 at approximately 4:07 P.M. I was at an elevation of 588 feet, ASL. I used a Canon PowerShot 14.1 Megapixel, SX210 IS digital camera for the photos.
The Draw the Sword site helped out by the NPS narrative and the SIRIS site offers the following description: Monument is a square rough cut granite shaft with a pyramidal top with incised letters and set on a seven foot square smooth finished base with incised letters. The shaft has an incised smooth panel with inscription. Overall height is 12.7 feet. Flanking markers are 1.6×1 foot. Monument marks the position held by the 19th Maine Infantry on July 3, 1863 as Longstreet’s Assault was launched.
The monument was dedicated October 3, 1889 by the State of Maine. The monument is composed of granite and has the following dimensions: The sculpture is 12 feet 7 inches and the base is approximately 1 foot 8 inches x 7 feet². There is a lengthy inscription on the front which read:
19th Maine Inf'y Reg't.
1st Brigade, 2d Division, 2d Corps
In the Evening of July 2d this Regiment at a position on the left of Batt'y C, 5th U.S. helped to repel the enemy that had driven in Humphreys' Division, taking one battle flag and re-capturing four guns.
On July 3, after engaging the enemy's advance from this position, it moved to the right to the support of the 2d Brigade and joined in the final charge and repulse of Pickett's Command.
Effective strength. July 2d. 405;
Killed & mortally wounded 65;
Wounded not fatally, 137; Missing 4.
Colonel Frances E. Heath.
The 19th Maine Infantry Regiment 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 monument is identified as structure number MN236-D.
From the Nomination Form:
1 of 15 mn to Maine. Indicates position held July 3, 1863 during Longstreet's Assault. 2 Pos. Markers indicate location July 2, in support Wier's Battery. LFlank &RF markers 65'&79' to mn, respectively. Pos. markers S of Mn nr Pleasonton Av, Mn W of Hancock Ave.
Short Physical Description:
Mn, 2 flank markers, 2 pos. markers. Mn base 7' sq smooth finish w/incised letters (added 1897). Sq granite shaft, rough cut w/incised smooth panel w/ inscription, pryamidal top w/incised letters. All 12'7"H. LF&RF 1'6"x1'x1'4"H. Pos. mkrs. 1'6"x1'1"x1'10"H.
Long Physical Description:
Monument that has two flanking markers and two position markers. Monument is a square rough cut granite shaft with a pyramidal top with incised letters and set on a seven foot square smooth finished base with incised letters. The shaft has an incised smooth panel with inscription. Overall height is 12.7 feet. Flanking markers are 1.6x1 foot. Position markers are 1.6x1.1 foot and 1.10 foot high. Monument is west of Hancock Avenue. Position markers are south of the monument near Pleasonton Avenue.
My Sources
1.
NRHP Nomination Form
2.
SIRIS
3.
Stone Sentinels
4.
Virtual Gettysburg
5.
Draw the Sword
6.
Historical Marker Database
7.
Wikipedia
8.
Find a Grave