Complex sentence: Arch Street Friends Meeting House, in Philadelphia, Pennsylvania, is the oldest meetinghouse of the Religious Society of Friends (Quakers) still in use in the United States and the largest in the world.
Split into simpler sentences: Arch Street Friends Meeting House, in Philadelphia, Pennsylvania, is a Friends Meeting House of the Religious Society of Friends (Quakers). It is the oldest meetinghouse of the Religious Society of Friends (Quakers) still in use in the United States and the largest in the world.