Photogrammar is one of the largest historical photo-mapping projects on the web. Because it covers such an intensely studied period of American history, it should be utilized often for  teaching and research at universities and K-12 schools. The visual materials of Photogrammar and Invincible Cities often overlap. The ships being constructed by cheerful workers in the OWI photos, and the machinery they used to make them, are rusting over in the world portrayed in Vergara's photographs. 

Lange and Vergara both use photographs of signs and graphics to capture the prominent happenings and prevailing attitudes in cities at different moments in time. Both websites display images of utter poverty. However, while Lange documents the movement of poor people from the countryside into cities, Vergara represents urban ghettos as a trap that precludes any mobility. When viewing Vergara's photos, it is easy to feel guilty about living comfortably in a society where these environments also exist. Lange's photos implore viewers to help the needy, but they do not accuse them of causing their distress. 

More than the other two sites, Los Angeles and the Problem of Urban Historical Knowledge offers new ways of thinking about the role of mapping in urban history. As an article in a peer reviewed journal, Ethington's project keeps a scholarly distance from its subject. Vergara's essays and captions express emotions in much less formal language than Ethington uses, thereby making his site much more approachable. Ethington and Vergara's projects are similar in their aim to bring visitors to their sites into urban spaces where they might not normally venture.