For a short period on Friday morning, the United States for the first time had a woman formally acting as president.

President Joe Biden, who turns 79 on Saturday, briefly transferred power to Vice President Kamala Harris, 57, when he was under anesthesia for a colonoscopy during a routine physical at the Walter Reed Medical Center, White House aides said. 

Harris worked from her office in the West Wing as she prepared for a trip to Columbus, Ohio, to talk about the bipartisan infrastructure package the president signed into law earlier this week. Biden is expected back at the White House in time for the annual pre-Thanksgiving turkey pardon ceremony Friday afternoon. (Peanut Butter and Jelly are the birds getting a reprieve this year).

Formal procedures for establishing succession of power when a president dies or is temporarily disabled did not exist until the 25th Amendment to the U.S. Constitution was ratified in 1967. Since then, presidents Ronald Reagan and George W. Bush briefly transferred power to their vice presidents. Biden is now the third.

Presidents invoking Section 3 of the 25th Amendment tell congressional leaders that they will be temporarily “unable to discharge the powers and duties of their office” and designate the vice president to perform them in their stead.

Before the 25th Amendment, however, there was Edith Wilson.

President Woodrow Wilson had a severe stroke in 1919 and, without clear guidelines about who should serve in his convalescence, his wife Edith Wilson began what she called her “stewardship.” For more than a year, until Woodrow Wilson’s term ended, Edith Wilson reviewed correspondence and decided what should be relayed to her husband. She also helped conceal the extent of his illness. 

The 25th Amendment has made the temporary transfer of power to vice presidents a more routine, and official, affair. George H. W. Bush was acting president for about eight hours while Reagan underwent surgery for colon cancer in 1985. Dick Cheney was acting president for George W. Bush in 2002 and 2007 — both instances lasted just over two hours and were also due to the president’s sedation during colonoscopies.

Harris was acting president for one hour and 25 minutes, the White House said.

Biden’s White House said it will release a written summary of his physical on Friday afternoon. It will be the first update on the president’s health since 2019, during his presidential campaign, when a doctor’s letter said he was healthy and “fit to successfully execute the duties of the presidency.” Biden was the oldest person to be sworn in as U.S. president.