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PHILADELPHIA (CBS) — Today is the 231st anniversary of the signing of the U.S. Constitution in Philadelphia. That means admission is free for The National Constitution Center today.

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Past presidents including Washington and Lincoln are scheduled to appear, there will be a student town hall with the Secretary of Education, Betsy Devos, and there will even be cake to celebrate!

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A 2014 survey by the Annenberg Public Policy Center at the University of Pennsylvania finds Americans know surprising little about the document.

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Think you could pass the test to become a U.S. citizen? Take a sample quiz here.