As of 2015, there is not a city name that occurs in all 50 states. The U.S. Geologic Survey's Geographic Names Information Service indicates that the name Riverside occurs in 46 states, the only exceptions being Hawaii, Alaska, Louisiana and Oklahoma.
The name Centerville is found in 45 states, and Fairview is in 43 states. There is a Franklin in 42 states and a Midway in 40.
Despite the fact that the name Riverside occurs in more states, there are more cities named Fairview and Midway in the nation, because some states have more than one city with the same name. Riverside is the name of 186 cities, but there are 273 cities with the name Fairview and 257 cities named Midway.