U.S. park rangers look at the spot where the Rev. Martin Luther King Jr. gave his famous “I Have a Dream” speech on the steps of the Lincoln Memorial in Washington, D.C., on Friday. Security threats have prompted officials to shut down the National Mall and much of downtown Washington, D.C.

WASHINGTON, DC – JANUARY 15: US Park Rangers look at the spot where Rev. Martin Luther King Jr. gave his famous I Have a Dream speech on the steps of the Lincoln Memorial with the Washington Monument in the distance on the morning of January 15, 2021 in Washington, DC. Due to security threats following the January 6th pro-Trump mob at the US Capitol, law enforcement agencies moved up security measures along the National Mall and much of downtown Washington, D.C. essentially closing down the Mall a week ahead of President-elect Joe Bidens inauguration. (Photo by Samuel Corum/Getty Images)