The 6th New York Cavalry was also known as The Ira Harris Guard (so named due to their benefactor, Senator Ira Harris). The regiment was raised in New York City, counties of Columbia, Steuben, New York, Dutchess, Renssalaer, Washington, Jefferson, Allegany, Broome, Monroe, and St. Lawrence. It was organized at Camps Scott and Herndon, Staten Island NY. The troopers were mustered in from September 12 to December 19, 1861. After the war, on June 17, 1865,the regiment was consolidated with the 15th New York Cavalry and was renamed the 2nd New York Provisional Cavalry. During the battle of Gettysburg, it served as a member of Devin’s Brigade in Buford’s Division of the Cavalry Corps, Army of the Potomac. The regiment was commanded at Gettysburg by Major William Elliott Beardsley (March 11, 1826 - December 25, 1884), a tailor from New York City. Under Beardsley's command @ Gettysburg the 6th Cavalry brought 407 men to the field and among them 1 was killed, 3 were wounded and 8 went missing. The troopers carried Sharps single-shot carbines, and .44 caliber Colt revolvers. On June 30, the unit was picketing the west side of Gettysburg holding back Confederate infantry until relieved by the Union First Army Corps on July 1st. It then shifted east to cover the York Road, eventually retiring to south of town near the Peach Orchard on Emmitsburg Road.
The monument is located on the right or east side of Buford Avenue @ Oak Hill, almost directly between Wadsworth/Buford Avenues and Mummasburg Road, along a straightaway, a rarity here at Gettysburg. The flank monument is 270 feet northeast of the primary 6th New York Cavalry Monument also located on the same side of the road. If facing the southeast, the 9th New York Cavalry left flank monument is to the left or northeast of this monument by about a foot or so. I guess these two units were lined up side by side on July 1, 1863. 
Parking is available at enlarged shoulder sections along the avenue. Stay off the grass less you be ticketed. I visited this monument on Thursday, July 5, 2012 at 10:03 AM, EDT, & @ an altitude of 604 feet ASL elevation.
Often, state regiment monuments are also accompanied by secondary monument which designate positions maintained from July 1-3, 1863 as well as flank monuments to delineate the ends of troop lines. This monument was dedicated on July 11, 1889 by the State of New York. The granite monument is about a foot square and almost a foot high like a rectangular prism, close to the road with a routed inscription on the top side of the monument. The sides are roughly hewn with smoothed edges and corners. The various sculptures for the cavalry unit was sculpted by James Edward Kelly (1855 - 1933) and fabricated by Beattie & Brooks and the Gettysburg-famous Frederick & Field companies. The brief inscription reads:
6TH
N.Y.C.
R.F.
The 6th New York Cavalry Monument and associated monuments and markers 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 monuments are identified as structures number MN003-B.
From the Nomination Form:
Marks position held by dismounted troopers of 6th New York Cavalry when they encountered Heth's CS Division July 1, 1863. 1 of 90 mn in Park honoring services of New York commands in Gettysburg Campaign. Located on Buford Ave, near its center.
Short Physical Description:
Mn & 2 flank markers. Composition of rough hewn & smooth stone. 25'9" high, 14'x10' base. Tower w/ turrets at each corner. Pilasters capped by horse heads. Bronze relief W face, 6'5"x5'8". Info tablet E face, 6'4"x3'11". Flank markers, 1'x1'x1'6".
Long Physical Description:
A monument that has two flanking markers. Composed of rough hewn and smooth granite. It stands 25.9 foot high on a 14x10 foot base. It has a tower with turrets at each corner. Horse heads caps the pilasters. A bronze relief is on the west face. Information tablet on the east side. Flanking markers are one foot square. Designed by Frederick and Field. Located near the center of Buford Avenue.
My Sources
1.
NRHP Nomination Form
2.
SIRIS
3.
Stone Sentinels
4.
Virtual Gettysburg
5.
Draw the Sword
6.
Historical Marker Database