Just a quick post to inform about a resource I just discovered.
If you have western Pennsylvania land owners in 1777 you have to check out this site. I have been trying to map the location of some deeds for my Philadelphia research on Johan Martin Rau/Rauh/Variants. This map had the deeds mapped out perfectly so I wish I had seen this over a year ago when I was struggling. You can zoom in and see the neighbors and even overlay a current map to help locate the property now. It also gave me the ability to browse by surname so I was able to find another land deed for him that was under a spelling I didn't even think to check.
Another issue I have had with my research is a location for Johan Martin's son-in-law and my ancestor, Abraham Hargis. A few years ago I found a 1781 tax list with him as an innkeeper in the Southwark area. Further research did not help me locate the inn but I did find Abraham mentioned in another list as being in South Ward with the same neighbors. When I started locating the neighbors on this landowner's map in South Ward I quickly noticed that there was an inn close to them. Not enough to prove that this was the one Abraham kept but it is enough to start researching the place. It also helped locate a free masons lodge very close to the inn. I have reference to him being removed from a lodge in Philly around the time he would have moved to Delaware. Knowing the location of the closest lodge gives me the opportunity to do more research into his freemason's link than a more generalized "all of Philadelphia" search.
If you check the about tab on the site it also gives you what sources they used to complete the map and links to further information about each one.