Fire insurance and real estate atlases offer one of the most incredible tools for researching urban form in the period roughly 1860–1940. However, these physical atlases can be cumbersome to use and difficult to compare across multiple volumes. Our Atlascope initiative has geotransformed 101 atlas layers of Boston and its inner suburbs and made them discoverable as never before on a custom new web interface, suitable for browsing on a computer or mobile device.