The Greater Philadelphia GeoHistory Network (GPGN) is a pilot project of the Philadelphia Area Consortium of Special Collections Libraries (PACSCL) to develop a web-based repository of geographically organized historical information about Philadelphia, its geography, its buildings, and its people.

Funding for the initial planning stage of the GPGN was generously provided by the Andrew W. Mellon Foundation, and we are exploring avenues for funding the full project contemplated by the planning group. See the Pilot Grant Report and the Next Steps Discussion (PDF) for more information on what we hope the project could become.

Meanwhile, the Athenaeum of Philadelphia, with the help of its partners, has continued to expand the collection of digital resources, particularly historic property atlases, available on this site.


The materials available on the GeoHistory site tend to be larger than your average scanner, requiring a larger-than-average solution. In addition, the original historic resources are often fragile and easily susceptible to damage and wear from standard large-format scanning techniques (for instance, blueprint scanners).

The overwhelming majority of items on this site were scanned by the Athenaeum of Philadelphia's Regional Digital Imaging Center (RDIC) using a Cruse Digital Scanner with a 4 foot by 6 foot synchronized scan table.

Maps are generally scanned at 300 or 400 dpi in 24-bit color, producing original TIFF files that each range from 250 MB to over 1 GB. Images are cropped, color corrected, and checked for overall quality.

The images are lastly compressed using wavelet technology such as JPEG2000 or ERDAS' ECW format. This allows the GeoHistory website to provide the user with an interactive viewer for zooming and moving around scanned images.


As conceived, the GeoHistory Network is about more than just maps. It's about providing the infrastructure and the information necessary to understand historic materials within the context of place and time.

To this end, GPGN hosted a conference in 2005 discussing many aspects of historical geography. The presentations and breakout transcripts of the Future Foundations: Mapping the Past conference are available here: