There are at least two civilian accounts concerning small arms fire on July 4. Both appear to relate to Confederates located along the small rivulet that runs along the eastern base of Seminary Ridge. Middle Street in Gettysburg is an east/west street one block south of the Diamond (or as we know it today, Lincoln Square).
Gates Fahnstock, who was 10 years old at the time of the battle, tells us that on July 4 it was dangerous to cross any of the east/west streets. His home was at the northeast corner of Middle and Baltimore Streets. In his narrative of his experiences, he tells of a bullet striking just above their heads when his family went outside on July 4 to start cleaning up the sidewalk.
Just one block to the west of the Fahnstock residence, on the northwest corner of Middle and Washington Streets, sits the home of Michael and Julia Eyster Jacobs. Michael was a professor of mathematics and chemistry at what was then Pennsylvania College (now Gettysburg College). Their 16 year old daughter, Mary Julia Jacobs, became the target of Confederate pickets on July 4. The story is told by her brother, Henry, who was just a few days short of his 19th birthday at the time.
The door of the Jacobs home faced south toward Middle Street, with an easy view of anyone traveling north on Washington Street. Just west of the town was a small run or creek, near the base of the hill that rises to Seminary Ridge. Confederate pickets in the area of the run had an easy shot down Middle Street at anyone crossing the intersection at Washington Street. And indeed they did fire on any Union soldiers moving along Washington Street. These were most likely 11th Corps units. Union patriot that she was, Miss Julia (it seems she was usually called Julia rather than Mary) stood in the doorway to her parents home calling out and warning Union men coming north on Washington Street, “Look out! Pickets below! They’ll fire on you!”
The Confederates pickets were apparently displeased by the youngster ruining their fun. So, girl or no girl, they took several shots at her. As Henry told the story, “ . . . bullets began to frame her where she stood . . . .” But Julia was not about to give up her post. She simply moved back a short way into the hallway. From there she was out of rifle shot of the Confederates, but could still easily continue to warn any Union men coming north along Washington Street. Henry says that this continued for about 30 minutes.
This may not be the skirmishing action that you are looking for, but these first hand civilian accounts confirm that the noise of gunfire around Gettysburg on July 4, 1863, was not related to any Independence Day celebrations.