What county is Alexandria VA in

The town of Alexandria is in the U.S. state of Virginia and Alexandria City County.

The town of Alexandria covers 39.9 km2, has 146,294 inhabitants (2012 census) and a density of 3,666.52 inhabitants per km2. The average altitude is 12 m. The current mayor of Alexandria is William D. Euille.

Does Alexandria VA have a county?
What county does Alexandria belong to?
What cities make up Fairfax County?
What percentage of Alexandria VA is black?