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, Independence Hall, and a thriving metropolitan area, and Pittsburgh, a busy inland river port and major center for educational and technological advance. The Pocono Mountains and the Delaware Water Gap provide popular recreational activities. Pennsylvania is one of the U.S.'s most historic states. Philadelphia is often called the cradle of the American Nation. It was here that the Declaration of Independence and the Constitution were drawn up by the Founding Fathers. The so-called "Pennsylvania Dutch" region in south-central Pennsylvania is another favorite of sightseers. Pennsylvania Germans, including the Amish and the Mennonites, dominate the area around the cities of Lancaster, York, and Harrisburg, with smaller numbers extending northeast to the Allentown-Bethlehem-Easton area and up the Susquehanna River valley. Some of the Old Order Amish have left the area, but many Mennonites remain, particularly in Lancaster County. Some adherents eschew modern conveniences and use horse-drawn farming equipment and carriages, while others are virtually indistinguishable from non-Amish or Mennonites.