The images filled television screens in the United States and around the world, forever marking Trump's presidency and legacy.
Chao, a labor secretary and deputy transportation secretary under previous Republican presidents, has led the department for four years.
In an interview with Reuters on Dec. 31, Chao had said she planned to remain on the job through Jan. 20.
On Thursday, she was at pains to say that "we will help my announced successor, Mayor Pete Buttigieg, with taking on the responsibility of running this wonderful department." Among those who were spurred to quit on Thursday was Mick Mulvaney, a former White House chief of staff who resigned his post as a special envoy to Northern Ireland.