1791 Historical Pennsylvania Counties Map
View Historical US County Boundary Lines on Google Maps. County boundaries change over time: this historical Google Maps tool contains the full dataset from the Newberry Atlas, helping to ensure you are searching in the correct county for the years you are researching.
Why would you want to see historical Google Maps? County boundaries in the U.S. have changed over 17,600 times since America was settled in colonial times! This historical counties tool built on Google Maps will help you make sure you’re searching in the correct county for the place and any historical date you are researching. Research with confidence knowing that this tool is built using the complete dataset of the authoritative Newberry Library’s Atlas of Historical County Boundaries project.
Quick Tips for using this 1791 Historical Pennsylvania Counties Map tool
Type any PRESENT-day place or address in the “Search places” box above the map*
OR: Zoom into your place of interest on the map
- Type any HISTORIC date or year in the “As of date” box and click Go! The date must be in the
format M/D/YYYY or can be just a 4-digit year.
Historical county boundaries will draw, and an information pane about the county of interest will appear at the top of the map. The information pane lists the historical county name at the blue dot, and provides details on the latest boundary change as of the date you typed, including reference to the particular statute that triggered the change. The latitude and longitude for the blue dot is also displayed.**
- Check the “Show historical county labels” checkbox in the lower left corner of the map to see the names of the historical counties on the map
- Optionally, check the “Show county chronology if this place…” checkbox in the lower left corner of the map to see a complete listing of every county boundary change for your chosen location from the date you typed back in time to original county formation
- Optionally, check the “Show present-day counties” checkbox in the lower left corner of the map to see present-day county lines (thin red lines) overlaid on top of historical county lines (thicker brown lines)
- Optionally, check the “Show present-day townships” checkbox in the lower left corner of the map to see present-day township boundaries (thin dark orange lines)
- Click the ◉ button in the upper right corner of the map to use your current location. Click the ◉ button again to automatically update your location every 1, 5 or 10 minutes (Monthly Contributors also get an option to update every several seconds).***
- Subscribe to receive notification of tool updates and usage tips
* You can also type in GPS coordinates in decimal degrees into the Search places box. For example, type -105.25,
40 for Boulder, Colorado.
** All information is reported based on the location of the blue dot on the map; to move the blue dot, click the map
*** The “Locate” button will be more accurate on smartphones and other devices containing a GPS; desktop browsers typically show an approximate location
FAQs for 1791 Historical Pennsylvania Counties Map
How do you see Google Maps with historical county lines? (This is often the tool people are searching for when they search for Randy Majors maps) Just follow the quick steps above and you will see the historical county boundary lines for anywhere in the U.S. displayed on a fully interactive Google Map.
Answer questions such as:
– What county was this present-day address located in as of this historical date?
– What county was my ancestor’s farm in as of this historical date?
– Which county’s archives or court house might have records for the time period I am researching?
– What county were these GPS coordinates located in at this historical date (see * above)?
Plus many other topics where knowing historical counties may be important, such as education, genealogy and historical research
Looking for PRESENT-day county boundaries on Google Maps? Here it is: County Lines tool.
Why was this tool created? Many people have requested to be able to see historical county lines from the Newberry Library’s Atlas of Historical County Boundaries displayed on top of Google Maps.
While some other tools can show the Newberry Atlas in GIS formats for Google Earth, requiring downloads and installation, this free tool shows the entire Newberry Atlas of Historical County Boundaries overlaid on Google Maps in a web browser. Therefore, you don’t have to download, install or import anything, and you can even use it on your smart phone or tablet.
Coverage Notes– Coverage includes all 50 US states, from as early as 3/4/1629 through 12/31/2000. For present-day county lines use the County Lines on Google Maps tool.
- The Search places box uses a standard Google Maps geocoding engine, therefore you can type PRESENT-day street addresses, road names, points of interest, and GPS coordinates (see * above) to see what county that location is part of
- NEW! Some counties or regions were claimed by more than one jurisdiction in some historic years. When this is the case, an “Overlapping jurisdiction” button will appear at the top of the map enabling you to toggle to the other jurisdiction’s information.
- The map layers from which this information is extracted are very large, so it may take several seconds to finish drawing
- Note that typing an address will zoom in the map very close, whereas typing a city or county by itself will show you a map with a wider view
- Disclaimer: While the number of decimals in the latitude and longitude displayed for the map marker may imply a positional accuracy of within a few feet, note that Google Maps and the source data may not be that accurate. Accordingly, this tool should not be used for legal nor surveying purposes or anything beyond entertainment value.
Sources– Atlas of Historical County Boundaries, a project of The Dr. William M. Scholl Center for American History and Culture at The Newberry Library in Chicago, Illinois. The information is included in this tool under the Creative Commons license shown on the bottom of the linked page.
– US Census Bureau
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Have a genealogy blog or website? Create your own custom link to this Historical U.S. Counties Map for any year and place
Listing of all Historical U.S. County Boundary Maps by state and year