PHILADELPHIA - Many ask, "How and When did the Liberty Bell crack?" The National Park Service explains that the crack was caused by more than 90 years of use and the bell's metallic composition. But what caused the crack? And how can we know? The researchers at Winterthur Museum believe that the high tin content contributed to the cracking. The cracks were not visible to the naked eye but were noticed by researchers when the bell was hung.

PHILADELPHIA - Did you know that the Declaration of Independence was signed in Philadelphia? If not, you are missing out on a very important history lesson. You can read about how it was written here. Jefferson is credited with being the principal author of the document. It affirms the July 2 decision of Congress to break away from Great Britain. Although the document's language may be stirring, not all Americans, males or white, can agree with the sentiments expressed within. The 2nd Continental Congress wrote it.

PHILADELPHIA - Having signed the U.S. Constitution in Philadelphia, James Madison and the other founding fathers debated the Constitution and its amendments. In Philadelphia, delegates from New Jersey, Delaware, and Maryland could hear and debate the proposals. Some delegates could not attend because they were in London or France or because they were too busy pursuing local affairs. Regardless of their reasons, it is obvious that they had serious disagreements over the U.S. Constitution.

PHILADELPHIA - The United States Constitution was ratified on December 7, 1787, by five states: Pennsylvania, Georgia, Connecticut, and Massachusetts. Other states opposed the document because it did not safeguard their basic political rights. All fifty states eventually ratified the Constitution, except for the District of Columbia. It was drafted by James Madison, who subsequently served as President of the United States from 1789 to 1794.

PHILADELPHIA - In 1776, 56 delegates from 12 colonies met in Philadelphia to address the Coercive or Intolerable Acts.  These acts were designed to punish the colonies for the Boston Tea Party. John Adams and Samuel Adams were delegated to the meeting. Peyton Randolph, a prominent Virginia leader and George Washington's close friend was elected as the first president of the Continental Congress. The group agreed to meet again on May 10, 1776, to discuss the Coercive Acts.

PHILADELPHIA - The Assembly Room is located on the first-floor of Independence Hall. The room was built around 1790 and is decorated in the era's style. The earliest known painting of the room is called Congress Voting Independence. It was painted by Robert Edge Pine in 1784 and finished by Edward Savage. Savage died before his engravings were finished. The Massachusetts Historical Society acquired the plate in 1859, and the engravings were printed the following year.

PHILADELPHIA - If you're interested in the history of America's founding fathers, explore the chair of George Washington at the National Constitution Center. It was used by the 55 delegates of the Continental Congress to draft the Constitution, and you can even sit in his chair today.

PHILADELPHIA - Explore Independence National Historical Park in Philadelphia and get a feel for the American Revolution.  It is a federally protected historic district that preserves important sites associated with our nation's founding history. While you are exploring Independence Park, you might want to do some historical research on your own. Here are some tips to help you plan a visit to the historic district. Enjoy your trip! And don't forget to take pictures! Listed below are some of the most fascinating sites in Philadelphia.

PHILADELPHIA - When exploring the Presidents' House Site in Philadelphia, it is essential to know its history. The house was demolished in 1832, and its foundations are embedded in the ground. The exhibit includes videos that tell the stories of enslaved people and text panels that shed light on slavery and the executive branch.

PHILADELPHIA - While visiting Independence Hall in Philadelphia, don't miss the Presidents' House Site, where George Washington, Thomas Jefferson, and John Adams lived.  You can also view a video that explains the history of slavery in America. In this exhibit, you will learn how enslaved people lived alongside early presidents. On the outside of the hall, you can explore the Presidents' House Site. There is no charge to explore the monument.