York County 1860 Shearer and Lake wall map is a another great resource
Two of my recent posts were on historical atlases, first the 1876 York County atlas reprinted with the 1903 York City atlas, and then on the atlases of some other Pennsylvania and Maryland counties available for use at the York County Heritage Trust Library/Archives. The originals were very popular from about 1870 into the early 1900s. They were prized for the detail, showing individual property owners as well as churches, schools, mills and other businesses.
Slightly preceding the handy atlases were the more unwieldy wall maps. They also showed the property owners and other features, but to get that detail, they had to be quite large. The York County 1860 wall map by Shearer and Lake is five feet square; the corresponding 1858 map for Adams County, by Hopkins and Converse, is 38 by 53 inches. I suppose that they were mostly hung in schools, public buildings and perhaps offices of large businesses. Originals of both the York County and Adams County maps are on the walls of the YCHT Library/Archives.
Some county wall maps have been reprinted, some as a smaller scale sheet and some as individual townships in atlas form. Some have been indexed and some have not. The 1860 York County map has been reprinted on one sheet and is available for purchase at YCHT. The resolution is fairly good. I have found it quite readable, sometimes using a magnifying glass.
Other 19th century county wall map reprints available for use at the YCHT Library/Archives include Adams County, 1858; Cumberland County, 1858 (1987), Franklin County, 1858 (1993) and combined Perry, Juniata and Mifflin Counties, 1863 (1979).
Images of many 19th century wall maps of Pennsylvania counties are also accessible on the Pennsylvania State Archives web site.