The position marker for the right flank of the infantry of the Army of the Potomac is southeast of Gettysburg on Neil Avenue, often called “Lost Lane” because of its inaccessability. (39.808015° N, 77.209404° W; Google map)
On July 3 Neill’s Brigade of the Sixth Army Corps was ordered to protect the Army of the Potomac’s main supply line on Baltimore Pike from Confederate skirmishers who were drifting down from the fighting around Culp’s Hill. Neill formed his brigade and advanced to the present location of Neill Avenue, driving back the Confederates while taking a handful of casualties.
The position marker is near the monument to the 61st Pennsylvania Infantry, which was the right flank of the brigade. The regiment’s right flank marker is next to the position marker.