Westerville, once known as "The Dry Capital of the World", is a city in Franklin and Delaware counties in the U.S. state of Ohio. The population was 35,318 as of the 2000 census, making Westerville then the largest suburb of Columbus. Westerville's population is estimated to have risen slightly to 35,739 as of July 1, 2007. The city is located at 40°7′25″N 82°55′17″W / 40.12361°N 82.92139°W / 40.12361; -82.92139 (40.123496, -82.921432).