In Virginia, local governments are divided into two top-level classifications: counties and independent cities.
Arlington is the fourth-largest county in Virginia by population — after Fairfax, Loudoun and Henrico — but by far the smallest, at only 26 square miles. In fact, Arlington is the smallest self-governing county in the U.S. (Mathews County, on the Chesapeake Bay, is the second smallest in Virginia, at 86 square miles.)