Arrow frequently relocates Starling City.
The first season placed Starling near Seattle because the series is filmed in Vancouver and the two cities have similar terrain. The second season flashed geographic coordinates that depicted Starling City’s airport in northern Wisconsin, somewhere north of Green Bay. Then during a Flash/Arrow crossover in the third season, they said that The Flash ran from Central City to Starling City and that Barry traveled 600 miles to do so. Even if Starling City exists in northern Wisconsin, Barry would still have had to travel more than 600 miles, so there may be a third location for Starling City. But the comics place Green Arrow in Star City and that’s in northern California.
As far as the Golden Age Flash’s home of Keystone City is concerned, it’s located across the Missouri River (in Kansas) and serves as a twin city for Central City, MO. I didn’t include it on the map because that would’ve looked crowded.
Metropolis used to be located near New York City but it got moved to Illinois. Many believe that it’s located in Chicago, and that may be, but DC Comics made a public announcement that the physical Metropolis is the official home of Superman. Perhaps I should’ve put a second Superman logo in northern Illinois to muddy up things further.
At any rate, let’s see how these locations compare in terms of population.
I guess Smallville’s population is no more than a drop in the bucket when compared with Metropolis. Ba-dum-bump.
Note: Gotham City’s population refers to post-No-Man’s Land arc.