Text on Maps has collected pieces of text from 57,000 georeferenced maps from the David Rumsey Map Collection and made them searchable with mapKurator, allowing users to search within the contents of text on maps, rather than just the metadata. From the site:
“While library patrons have become used to searching books via their content as well as their titles and authors, such technology has not yet been applied to visual media like maps. Exposing text on maps alongside traditional catalog record metadata transforms how people search maps and why people might be interested in historical maps altogether: now the content of large sets of maps can be examined as data that tells us not only about the history or cultural context of specific places, or of regional mapping traditions, but also about broader social and cultural developments.”
Text on Maps Help Guide provides documentation for searching, viewing, and becoming a contributor through transcription, georeferencing, and annotating.