How do young children figure out that markings can be used as symbols for things in the world? Three studies used a map-reading task to examine the role that labeling plays in cueing children into the referential use of markings. Study 1 reports a striking failure among toddlers to use abstract maps as representations for a set of familiar objects when object labels were not given for the markings. Children succeeded, however, when labels were provided, and when the images in the maps were realistic-looking (Study 2), children succeeded whether or not object labels were given. As this could owe to covertly labeling the familiar images rather than the perceptual similarity between the images and objects, a third study used realistic images of novel objects, and found that children succeeded only when labels were provided. Labeling appears to be an important source of evidence to the referential function of markings.