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County road maps are available in most if not all courthouses. Older maps are published in county histories, county atlases, and in manuscript collections such as at the Historical Society of Pennsylvania, the state library, the Free Library of Pennsylvania (Logan Square, Philadelphia, 19103), the Carnegie Library at Pittsburgh, and the Pennsylvania State Archives. For the latter see Martha L. Simonetti, comp., Descriptive List of the Map Collection in the Pennsylvania State Archives, edited by Donald H. Kent and Harry E. Whipkey (Harrisburg, Pa.: Pennsylvania Historical and Museum Commission, 1976), and online at www.phmc.state.pa.us. Useful city maps can sometimes be found in city directories. An interesting map showing the development of the Commonwealth’s counties is available for a nominal fee from the Pennsylvania Historical and Museum Commission, Publication Sales Program, 400 N. St., Harrisburg, PA 17120-0053. See also Henry F. Walling and O. W. Gray, 1872 Historical Topographical Atlas of the State of Pennsylvania (1872; reprint, Knightstown, Ind.: Bookmark, 1977), which has business directories and a place-name index. A wonderful publication, The Atlas of Pennsylvania, edited by David J. Cuff and others (Philadelphia: Temple University Press, 1989), goes beyond its maps in providing a “geographical encyclopedia.”
Available at the state archives (with copies at the state library and the respective county recorders of deeds) are warrantee maps for twenty-four counties. Those for Fayette, Greene, and Washington were also published and indexed in volume 3 of The Horn Papers by W. F. Horn (New York: Hagstrom Co., 1945), but the preceding two volumes of text are mostly fiction (see William & Mary Quarterly, series three, 4 : 409-451). Allegheny County Warrantee Atlas was published by the Western Pennsylvania Genealogical Society (Pittsburgh, 1982; reprint 2003).