Founded as William Penn's "Holy Experiment," Philadelphia has a centuries-long history of fostering and constructing prominent houses of worship throughout the city. In recent decades, as congregations face declining membership and shifting neighborhood demographics, these historically- and architecturally-significant properties have often suffered from deferred maintenance, insensitive alterations, and partial or complete demolition.

Advocacy organizations like the Preservation Alliance for Greater Philadelphia and Partners for Sacred Places have focused on this issue for years, highlighting the threats to Philadelphia's neighborhoods and communities if these structures continue to be abandoned or lost. Over the summer of 2011, in order to more fully understand and address the issue, the Preservation Alliance partnered with Philadelphia Historical Commission and Partners for Sacred Places to develop a comprehensive index of historic churches covering the entire city. Compiling, verifying, and updating data from a number of different sources, University of Pennsylvania graduate student Molly Lester assembled a database which includes every purpose-built house of worship constructed in the city before 1960.

Data elements include: current congregation, original congregation, address, year of construction, original architect and whether or not the build is on the Philadelphia or National Historic Registers.