Opal City
Opal City is a fictional city set in the DC Universe. Created by James Robinson and Tony Harris in 1994, "the Opal" has been established as the home of several DC Comics characters, most notably several super-heroes who have operated under the name of Starman.
Opal is particularly notable for several aspects of its depiction in the second Starman series, including its history as established by Robinson dating back to early Puritan settlements on the eastern shores of North America under the name "Port o'Souls", as well as its architectural stylings as established in Harris' work as that series' initial artist.
Recent issues of the current Justice League of America series, specifically the "Crisis of Conscience" arc, have explicitly established Opal City as being located in Maryland, per Robinson's longstanding opinions on the subject in various interviews with fans.