<p>Maphub is a web portal for georeferencing and annotating digitized historic maps. Georeferencing transforms the map image to align with real world geographic coordinates, while the annotations are overlaps plus notes. Maphub suggests possible tags for the annotation based on its text and location; tags link to related Wikipedia articles.  Once created, user-contributed annotations are shared via the Maphub Open Annotation API.</p><p>A first prototype of Maphub, using digitized maps from the Library of Congress’ Map Division, can be found at http://maphub.herokuapp.com/.</p>