During World War II, the U.S. carried out the secret Manhattan Project, which led to the creation of the atomic bomb. Thousands of scientists across the country, including Dr. Chien-Shiung Wu, worked on the project. Today, Manhattan Project National Historical Park preserves three locations of their work in Tennessee, New Mexico, and Washington. Note: many areas in the park are not currently open to the public, so make sure to check the park’s website before planning your visit.