OldInsuranceMaps.net started as a master’s thesis project in 2022, but has continued to grow since then, becoming a well-used collaborative platform for georeferencing historical Sanborn fire insurance maps from the digital collection at the Library of Congress. OIM provides a comprehensive workflow for ingesting, splitting, georeferencing, and mosaicking entire atlases, creating geospatial raster datasets along the way that can be freely downloaded or accessed via a number of different web mapping service endpoints. To date, over 30,000 map pages have been georeferenced by various research teams and individuals across the US, covering (or partially covering) almost 375 different cities and towns. This talk will introduce the platform, go for a deep dive into details about how the open source software stack, data structure, and file storage management has evolved over time.