Pennsylvania (the Commonwealth of Pennsylvania) is one of four states of the United States of America that is called a commonwealth. It has given its name to the Pennsylvanian time period in geology. Pennsylvania is called the Keystone State. Although Swedes and Dutch were the first European settlers, the Quaker William Penn named Pennsylvania for the Latin phrase meaning "Penn's woodlands", in honor of his father. Today, two major cities dominate the state - Philadelphia, home of the Liberty Bell, Constitution Hall, and a thriving metropolitan area, and Pittsburgh, a busy inland river port.