Baltimore is the biggest city in the U.S. state of Maryland. In 2010 it had about 620,961 people living there. It is not in any county, so it is called an independent city. It is next to the Chesapeake Bay and used to be an important port for trade by ships. There is still some shipping but the Inner Harbor is now mostly famous for shopping and restaurants, and also for the National Aquarium and other museums.