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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.

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!

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

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