Waldo, Arkansas. Waldo is a town in Columbia County, Arkansas, United States. The population was 1,372 at the 2010 census.
Reston is a census-designated place (CDP) in Fairfax County, Virginia, United States, within the Washington, D.C. metropolitan area. The population was 58,404, at the 2010 Census and 56,407 at the 2000 census.
265,765 Contributions.   Answer   The largest county in Virginia by size is Pittsylvania County with an area of 978 square miles. The largest county by population, as of 2005, is Fairfax Câ¦ounty with a population of 1,006,529.     I believe that pittsylvania county in the center of southern VA is the biggest.