Montgomery County of the U.S. state of Marylan is situated just north of Washington, D.C. and southwest of Baltimore. It is one of the most affluent counties in the nation, and has the highest percentage (29.2%) of residents over 25 years old that hold an advanced degree. The county seat and largest municipality is Rockville. Most of the county's residents live in unincorporated locales, the most populous of which is Silver Spring. It is a part of both the Washington Metropolitan Area and the Baltimore-Washington Metropolitan Area.