Residual haunting is the term often used within the paranormal community to refer to the ghostly images of certain people or events that may be repeatedly seen in a particular place over a long period of time. It's often been thought that perhaps these images may represent some kind of psychic "trace" or remnant of those people or events that has somehow been left at that particular place, and which continues to linger or persist throughout the years (hence the basis for the term). 
Sometimes these residual hauntings seem to reflect particular moments from history, such as the American colonial struggle for independence (for which the 4th of July is celebrated in the United States). That would appear to be the case for the haunting occurrences that have been reported at the General Wayne Inn in southeastern Pennsylvania, which was first built in 1704. Before being used as a military outpost during the American Revolution, the inn had hosted one of the earliest known post offices in the U.S. (headed by colonial postmaster Benjamin Franklin). It is also said that Edgar Allan Poe had been making revisions to his famous poem "The Raven" while staying at the inn in 1836.
The earliest known residual haunting experience reported at the General Wayne Inn dates back to 1848, when it was serving as a local township polling site during that year's election. At one point, the polling site overseer had asked a woman to go down to the cellar to gather a fresh batch of ballots. When she came back up the stairs, the woman said that while she was down there, she'd seen the spectral figure of a soldier wearing a green coat with yellow lapels. It was later learned that this color scheme was the same one found on the uniforms worn by Hessian soldiers during the Revolution [see the image below] (the Hessians were German mercenaries who were hired to fight on the side of the invading British army). Further sightings of this same ghostly soldier were occasionally reported by various members of the inn's staff in the years that followed.
Another intriguing encounter with a ghostly soldier was reported by a former hostess of the inn. In recalling this experience, she stated that:
"It was around...3:30 in the afternoon, and I was setting up for dinner. And I heard someone calling me - just my name...I heard this three or four times. But I was so engrossed in setting up the table. I turned to say - I was getting a little angry, too - and I turned to say, 'What do you want?' I saw this man...He was a man standing on the stairs, and he had this uniform on...a Revolutionary War soldier, only to me he was like a general...And he looked so startled when I said, 'What is it?' And just like that, he disappeared." [2, p. 368]
Later on, she added:
"I would say it was three-dimensional...The figure that I saw on the stairs was not transparent. I couldn't see through the figure, and that's what startled me so...The bartender...looked at me and he said, 'What's the matter? You look like you saw a ghost.' And I said, 'Well, I think I did.'" [2, p. 369]
When asked her thoughts about the significance of the experience, the hostess said:
"I thought he was calling me...He called me three or four times...like he wanted...some help or something...I never thought for a minute that it was a hallucination or the light or anything. There was no shadows or the sun didn't hit the stairs...I have no explanation for it whatsoever...I just know it happened." [2, p. 369]
A number of other seemingly mysterious phenomena have reportedly been experienced at the General Wayne Inn over the years, and several of them are illustrated in a profile segment on the inn that was made in the late 1980s for the popular television show Unsolved Mysteries. A video clip of that segment (which has been slightly re-edited from the original that was filmed back in August of 1988, and is narrated by actor Dennis Farina) can be viewed on YouTube:
If residual hauntings do happen to represent some kind of psychic "trace" lingering at a certain location, then could mediums and psychics possibly pick up on that "trace" when visiting the location? As seen in the video clip, parapsychologist Michaeleen Maher had conducted an investigation at the General Wayne Inn in August of 1988 , and her findings may offer us some possible insight into that question. Using an ingenious field investigation technique that was first developed and applied by her teacher, the late parapsychologist Gertrude Schmeidler, in the 1960s , Maher had sought to test the impressions that three mediums and psychics seemed to receive as they each walked through the General Wayne Inn one at time, when none of the inn's staff were present.
Going from floor-to-floor and room-to-room, the mediums and psychics were asked to try and psychically "sense" the specific areas in the inn where the staff and other witnesses had seen ghosts or experienced other kinds of haunting phenomena. Whenever they felt that they'd come across such an area, they were asked to mark it down on a blank floor plan that had been made of the inn's interior.
Later, as a control comparison, Maher asked three non-psychics (people who did not profess to have any psychic ability, and who tended to be skeptical towards the existence of ghosts) to walk through the inn and try to locate these same areas, as well. These non-psychics mainly tried to do this through simple guessing and by judging how dark and "spooky" some areas of the inn seemed to look or feel.
Once all of this was complete, Maher statistically compared the areas that the mediums and psychics had marked on their floor plans with those that the staff and other witnesses had marked out on separate floor plans. In at least one instance, she found that the areas marked by a psychic seemed to closely correspond to those marked out by the staff and other witnesses to a statistically significant degree, with odds of about 40 to 1 against chance.  Moreover, the combined responses of the mediums and psychics seemed to come rather close to corresponding with the areas marked by the staff and other witnesses, to a statistically suggestive degree (odds of about 12 to 1 against chance).
In stark contrast, when Maher compared the areas marked by the non-psychics to those marked out by the staff and other witnesses, no statistically significant correspondences between the two were found. These findings begin to suggest that the mediums and psychics were moderately successful at being able to "sense" the "haunted" areas of the inn, whereas the non-psychics were not.
Maher had conducted similar investigations at four other allegedly haunted locations using this technique, and she obtained notable statistical findings in at least two of them. When all of the statistical data from these investigations were combined together, they generally indicated that, on the one hand, the mediums and psychics were indeed able to "sense" the areas where witnesses had seen ghosts or had unusual experiences to a statistically significant degree, with odds of about 1,000 to one against chance. Non-psychics, on the other hand, were generally not successful in picking out those areas. 
These findings hint at the possibility that the mediums and psychics were responding to something at these allegedly haunted locations. Could it have been the ghosts that are thought to still linger there? These findings don't clearly tell us that, but that possibility hasn't yet been fully ruled out, either. Perhaps additional research will one day shed further light on this issue.
The PRF would like to wish everyone a happy and safe 4th of July weekend!
References & Notes:
 For a concise overview of residual haunting (and how it might tie into the parapsychological concept of "place memory"), see the related PRF blog entry at: https://www.psychicalresearchfoundation.com/single-post/2015/12/12/Place-Memory-Residual-
 Maher, M. C. (2000). Quantitative investigation of the General Wayne Inn. Journal of Parapsychology, 64, 365 - 390.
 Schmeidler, G. R. (1966). Quantitative investigation of a "haunted house." Journal of the American Society for Psychical Research, 60, 137 - 149.
 For reference, an odds ratio of 20 to 1 is commonly taken as being a statistically significant finding in the social and behavioral sciences (which include psychology and parapsychology).
 Maher, M. C. (1999). Riding the waves in search of the particles: A modern study of ghosts and apparitions. Journal of Parapsychology, 63, 47 - 80.
[Source images: Unsolved Mysteries]