Virginia is full of places that are referred to as one thing, have a zipcode for another thing and are unincorporated. Everyone refers to the place where the CIA is as "Langley" and it butts right up against McLean.
McLean is within Fairfax County.
Virginia also has (I think) 23 independent cities that are not IN a county at all. Fairfax City is surrounded by Fairfax County, but is a separate entity. Yeah, it's weird.
Only other independent cities are Baltimore Maryland and St. Louis Missouri.