Official website of the Smithsonian, the world's largest museum and research complex, with 19 museums, 9 research centers, and affiliates around the world.

Where they're located: Washington D.C., Washington, D.C., USA
Website traffic: 5.93M/month

4. National Constitution Center – constitutioncenter.org

The National Constitution Center in historic Philadelphia is America's most hands-on history museum. Located just two blocks from the Liberty Bell and Independence Hall, it is the only museum devoted to the U.S. Constitution and the story of we, the people.

Where they're located: Philadelphia, Pennsylvania, USA
Website traffic: 760K/month

5. United States Holocaust Memorial Museum

Website traffic: 2.41M/month