The 1st New York Artillery, Battery B was also known as The Empire Battery. During the battle of Gettysburg, it served as a member of Hazard’s Brigade in the Second Corps, Army of the Potomac. The battery was commanded by Captain James McKay Rorty (1837-1863). Rorty was a book canvasser in New York City, a job he described as "crippling my intellect". He wounded at Fredericksburg and killed on July 3 during the final day of battle of Gettysburg. Rorty was buried close to where he fell. A few weeks later Richard Rorty, James' brother, came to Gettysburg and returned his body to New York, where it was laid to rest among many other Irish heroes of the Civil War in Calvary Cemetery. Under Rorty's limited command, 114 men (and 20-pounder Parrott rifles) were engaged at Gettysburg and among them 10 men were killed and 16 were wounded.
The 15th Massachusetts Infantry Monument is located on the left or west side of 
Hancock Avenue (RD310) if traveling north along the road at the beginning of an area called The Angle. The sculpture is flanked on either side by two reproduction 20-pounder Parrott rifles. This monument is part of a string of monuments that extend a hundred feet or so south and north (west of this position) across the green field to the United States Regulars Monument (MN235) 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. 
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 3:48 P.M. I was at an elevation of 581 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: Marker on low rough-hewn base has a Parrot rifle cannon barrel on each corner and is topped with a II Corps trefoil. There is a relief plate of the New York State seal. It marks the position held by the 1st New York, Rorty’s Battery B, on July 3, 1863.
The monument was dedicated June 3, 1888 by the State of New York. The monument is composed of Quincy granite with brass (of all things) and has the following dimensions: The sculpture is approximately 9 feet x 38 inches² and the base is approximately 20 x 81 inches². The sculpture was fabricated by the Frederick & Field. This company is credited with scores of monuments throughout the Park. There are inscriptions on tall four sides of the monument which read:
(Front):Battery B
1st New York
Light
Artillery,
Artillery
Brigade,
2d Corps.
(Back):Position held
afternoon of
July 3d 1863.
Casualties;
Killed 10,
Wounded 16.
(Left):Mustered
into service
Aug. 31, 1861.
participated
in 78 days
of battle.
Mustered out
of service
June 16, 1865.
(Right):Organized at
Baldwinsville
Onondaga Co.
New York.
The Battery B, 1st New York Artillery Monument 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 MN240-D.
From the Nomination Form:
1 of 90 Mn to New York. Indicates position held July 3, 1863 during Lonstreet's Assualt. LF&RF at 41'&43' N-S to mn, respectively. Cannons N-S of Mn. Mn located W side of Hancock Ave.
Short Physical Description:
MN w/2 wrought-iron rifled cannon mounted on cast-iron carriages & 2 markers.
Long Physical Description:
Base stepped 6'8" sq, 2nd part rough cut. 2 part granite shaft, 2nd part 4 inverted cannon tubes at corners, 4 sides w/excised polished inscriptions, topped w/bronze medallions & 2nd Corps trefoil symbol. All 11'H. LF&RF 1'sq x 1'6"H
My Sources
1.
NRHP Nomination Form
2.
SIRIS
3.
Stone Sentinels
4.
Virtual Gettysburg
5.
Draw the Sword
6.
Historical Marker Database
7.
New York State Military Museum