The 4th Pennsylvania Cavalry served as a member of Gregg’s Brigade in Gregg’s Division of the Cavalry Corps, Army of the Potomac. The cavalry was commanded by Lieutenant Colonel William E. Doster (1837-1919). Doster was a law student at the beginning of the Civil War. He enlisted in the Army and was appointed a Captian in the Pennsylvania Cavalry Corps. In 1862, he was promoted Major in 4th Pennsylvania Cavalry, Army of the Potomac and participated in the Antietam Campaign. At the Battle of Gettysburg in July 1863, he was a Lieutenant Colonel in command of regiment in support of a battery of field artillery when he distinguished himself in successful repel of Confederate forces at the Union rear flank. For actions at Gettysburg, he was brevetted Brigadier General of US Volunteers. Under Doster's command, his unit has 307 men engaged at Gettysburg, and among them, 1 was killed.
The 4th Pennsylvania Cavalry is located on the right or east part of Hancock Avenue if traveling north toward the Pennsylvania Monument which looms hugely in the distance. This part of the battlefield is the south section of Cemetery Ridge. 
Parking is available at small, cutout shoulders along the road, some wide, some narrow. Be sure to stay off the grass or you will be ticketed by park police. I visited this monument on Thursday, July 5, 2012 at approximately 5:45 P.M. I was at an elevation of 601 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: A mounted cavalryman in relief appears in the front recessed area of a commemorative marker. The marker is square with an apexed top and stands on a tiered, rough-hewn base. The marker is rough-hewn on the sides and smooth at the top and the back. The figure and horse are full-length, and the figure holds a sword upright in his proper right hand. A Pennsylvania State Seal in bronze is located below the relief. Monument is a two-part granite shaft with a gable peak and set on a 9.3×4.3 foot rough cut base. The lower part of the shaft is incised granite framing a bronze bas-relief plaque and the upper part is an excised bas-relief extending to the gable. Overall height is 9.6 feet. Flanking markers are one foot square.
The monument was dedicated on September 11, 1889 by the Commonwealth of Pennsylvania. The monument is composed of Westerly blue granite with bronze elements and has the following dimensions: Overall: The sculpture is approximately 9 feet x 7 feet x 2 feet and the base is approximately 4 feet 2 inches in by 9 feet x 4 feet. The monument was fabricated by Dalbeattie Granite Works. There are inscriptions on the front and reverse side which read:
(Front):4th Pennsylvania Cavalry
3rd Brigade.
2nd Division.
Cavalry Corps.
Army of the Potomac.
(Back):Detached on the morning of July 2nd. from the Brigade at the
junction of White Run and Baltimore Turnpike. Ordered to
report to Head Quarters, Army of the Potomac.
Supported a Battery temporarily near this position.
on picket at night. Returning late in the afternoon of the 3rd to
Second Cavalry Division.
Mustered in Aug. 15 to Oct. 30, 1861 Re-enlisted Jan. 1, 1864
Mustered out July 1, 1865
Recruited in Northampton, Allegheny, Westmoreland, Indiana,
Venango, Lebanon, and Luzerne Counties
Total enrollment 1930Killed and died of wounds officers 9 men 92 Total 101
Died of disease etc. officers 3 men 252 Total 255
Wounded officers 21 men 248 Total 269
Captured or missing officers 5 men 266 Total 271Total casualties 896
From Mechanicsville June 26, 1862
to
Appomattox April 9, 1865.
The 4th Pennsylvania Cavalry 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 MN266-B.
From the Nomination Form:
1of 110 Civil War monument to Pennsylvania of GBMA Era (1863-1895). Indicates position of 4th PA Cavalry evening Jul 2, 1863. LF&RF markers located 136' & 26,' respectively N-S of mn. Mn located E side of Hancock Avenue, S of Humphreys Ave.
Short Physical Description:
Mn & 2 flanking markers. Base 9'3"x4'3," rough-cut. 2 part shaft, 1st: incised granite framing bronze bas-relief plaque. 2nd: excised bas-relief, extending to gable peak. All 9'6" H. LF&RF markers 1'sq x 1'5"H.
Long Physical Description:
Monument that has two flanking markers. Monument is a two-part granite shaft with a gable peak and set on a 9.3x4.3 foot rough cut base. The lower part of the shaft is incised granite framing a bronze bas-relief plaque and the upper part is an excised bas-relief extending to the gable. Overall height is 9.6 feet. Flanking markers are one foot square. Located on the east side of Hancock Avenue, south of Humphreys Avenue.
My Sources
1.
NRHP Nomination Form
2.
SIRIS
3.
Stone Sentinels
4.
Virtual Gettysburg
5.
Draw the Sword
6.
Historical Marker Database
7.
Find a Grave