The 73rd New York Infantry was also known as Second Fire Zouaves. The regiment was organized in New York City in May 1861 as a Zouave regiment, known for its unusual dress and drill style. The uniform worn by this regiment consisted of the New York state jacket, sky blue trousers with a red stripe down the seam, tan gaiters, and a red Zouave fez with a blue tassel. Drawn from the ranks of the city's many volunteer fire companies, the unit was known alternately as the Second Fire Zouaves, after the 11th New York was known as the First Fire Zouaves. During the battle of Gettysburg, it served as a member of Brewster’s “Excelsior” Brigade in Humphreys’ Division of the Third Corps, Army of the Potomac, A Fighting 300 Regiment. The unit was commanded by Major Michael William Burns (1834-1883), a city inspector and fireman from New York City. He was wounded during the Second Manassas Campaign. Under his command, his regiment had 507 men engaged @ Gettysburg and among them 51 were killed, 103 were wounded and 8 went missing.
This infantry unit was part of the Excelsior Brigade which served in Humphreys’ Division of the Third Corps, Army of the Potomac. The 70th, 72nd, and 74th Were Fighting 300 Regiments. The 70th New York commanded by Col. John E. Farnum (1824-1870); engaged 371; 20 killed, 93 wounded, 4 missing. 71st New York commanded by Col. Henry L. Potter (1828-1907); engaged 243; 10 killed, 68 wounded, 13 missing. 72nd New York commanded by Col. John S. Austin (1817-1865); engaged 366; 7 killed, 79 wounded, 28 missing. 74th New York commanded by Lt. Col. Thomas Holt (1831-1897); engaged 275; 12 killed, 74 wounded, 3 missing.
The 73rd New York Infantry position marker is located in a field at a fence line along Sickles Avenue, on the left or west side of the road if traveling north along the road. To the east of this position is Millerstown Road, to the south, Route 15 and to the west and United States Avenue to the north. This area is called Excelsior Field, near stop 10 of the Gettysburg Driving/Audio tour. The Peach Orchard is just to the southwest of this position. The primary monument for the 
New York Excelsior Brigade (MN184-E) lies 56 feet east (96°) of the position marker. There are a total of five position markers associated with this brigade, all looking exactly the same and no flank markers. Parking is plentiful and available at intermittently enlarged shoulder cutouts on the right side of the road. Be sure to keep vehicles off the grass or you will be ticketed by park police. I visited the monument on Thursday, July 5, 2012 @ 4:24 PM, EDT & @ an altitude of 586 feet, ASL. I used a Canon PowerShot 14.1 Megapixel, SX210 IS digital camera for the photos.
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. Presumably, the position markers were dedicated at the same time as the primary brigade monument, July 2, 1893. All the position markers are composed of granite with the incised inscription found on the top. The marker are all 2'6"x1'8"x1'8". Additional details from the nomination form concerning the flank monuments may be found below in red. The inscription reads:
73rd
N.Y.I.
Sickles
Brig.
The New York Excelsior Brigade Monument & 73rd New York Infantry Position Marker 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. Collectively, these monuments are identified as structures number MN178-E.
From the Nomination Form:
1 of 90 mns in Park honoring NY commands in Gettysburg Campaign. Marks position of 5 regiments of NY Excelsior Brigade on July 2, 1863 when it supported US troops on Emmitsburg Rd. Located on W side of Sickles Ave between Wheatfield Rd & US Ave.
Short Physical Description:
Mn & 5 position markers. Pentagon base, 6'2" each side, 21'7" high. Bronze tablets on each side of base, 4'3"x1'10". Bronze tablets on frieze, 5'6" in dia & 1'6" high. Granite domed cap w/ bronze eagle. 2'9" high. Position markers, 2'6"x1'8"x1'8".
Long Physical Description:
Monument that has five position markers. Granite monument is a five-sided base of which each side is 6.2 foot and capped with a granite dome with bronze eagle. Bronze tablets are located on each side of the base and are located on the frieze. Overall height is 21.7 foot. Designed by Theodore Bauer. Position markers are 2.6x1.8 foot. Located on the west side of Sickles Avenue between Wheatfield Road and United States Avenue. Position markers designate the locations of five regiments of the Excelsior Brigade, all west of Sickles Avenue between Wheatfield Road and United States Avenue.
My Sources
1. NRHP Nomination Form
2. Stone Sentinels
3. Virtual Gettysburg
4. Draw the Sword