Speaking of georeferencing old maps, the Leventhal Map Center at Boston Public Library has a collection of late 19th- and early 20th-century urban atlases. Their Atlascope platform presents 101 of them in a web interface overlaid on a modern street map. The Leventhal is now looking to expand Atlascope’s coverage beyond the Boston area to towns and counties across Massachusetts, and is raising funds to do so (it can apparently take 60 hours to process one atlas). Details on sponsoring an atlas here. See their Instagram post.