If you're here, you know what this is for. If you somehow ended up here, feel free to help out if you know about DC Comics. The rules are on the first page.
Locations in the DCU are all over the place so I did some research and came up with this:
Gotham City: New Jersey
Metropolis: Delaware
I found this to be consistent through many websites and although Wikipedia is not my favorite site to rely on, it phrased it the best way:
"The distance between the two cities has varied greatly over the years, ranging from being hundreds of miles apart to Gotham and Metropolis being twin cities on opposite sides of Delaware Bay, with Metropolis in the location of Delaware and Gotham City being in New Jersey."
