As this blog post from the Library of Congress notes, the US Constitution turns 220 years old today. It was ratified on September 17, 1787.
According to this Britannica Article, the US Constiution is the world’s oldest written national constitution that is still in use.
In honor of this anniversary, I’d like to send along these links from the library catalog:
Constitutions — United States
Constitutional Amendments
Constiutional History