"Arlington is the smallest, most densely populated county in the United States. Its destiny has been driven by its geographic proximity to Washington, D.C., and very important by the fact that most Potomac River crossings begin in the county. Initially part of a large land grant to Lord Fairfax before the Revolutionary War, what is now Arlington was ceded to help form the new federal government seat by the Commonwealth of Virginia in 1790. It remained...

RG 18 houses the collected papers of Barbara Marx, a local civil rights advocate who worked for the desegregation of Arlington schools during the 1950's.