If you spot the ground moving around Fifth and Arch Streets in Center City on Thursday, it just might be Ben Franklin turning over in his grave.

We can only imagine what the inventor, scientist, writer and Founding Father would think of the State Department's announcement Thursday that the United States will withdraw from UNESCO, the United Nations Educational, Scientific and Cultural Organization.

Independence Hall, where the Declaration of Independence and the Constitution were signed, is one of just 23 UNESCO World Heritage Sites in the United States. Other sites include the Statue of Liberty, Yellowstone National Park and Mesa Verde National Park.

Mayoral spokeswoman Lauren Hitt said in a statement Thursday that the city was "disappointed by the decision" and officials are trying to determine what, if any, effect it will have on Philly's World Heritage site and status. Media requests to UNESCO's New York City field office were directed to a spokesman in Paris, who was not immediately available.

In 2015, Philadelphia was named the first World Heritage City in the United States. World Heritage cities must have a UNESCO World Heritage site and have made an important impact on world history. The Organization of World Heritage Cities, a nonprofit which bestows the designation, is not a part of UNESCO but sometimes partners with the organization.

In a statement Thursday, U.S. Department of State spokeswoman Heather Nauert said the decision to withdraw, which will not go into effect until Dec. 31, 2018, rises from U.S. concerns "with mounting arrears at UNESCO, the need for fundamental reform in the organization, and continuing anti-Israel bias at UNESCO."

Irina Bokova, director-general of UNESCO, said in a statement Thursday that she regretted the U.S. decision but still believes UNESCO's many missions are "shared by the Americam people."

"The American poet, diplomat and librarian of Congress Archibald MacLeish penned the lines that open UNESCO's 1945 constitution: 'Since wars begin in the minds of men, it is in the minds of men that the defences of peace must be constructed.' " Bokova wrote. "This vision has never been more relevant."

Her statement also included a reference to Philadelphia's World Heritage Site.

"Independence Hall, where the Declaration of Independence and the Constitution were signed, is a World Heritage Site, because its message speaks to policy-makers and activists across the globe," Bokova wrote.