To my knowledge no SecState has become President or acting President in an official capacity.
Not true. Also, Haig had said something to the effect that he was “in charge, here at the White House” after the assassination attempt. The media ran with it claiming that Haig had claimed that he was President for that period.
Haig didn’t become acting president. His line, “I’m in charge here,” which I took to mean he was trying to keep things under control at the White House while Bush was traveling, was mistaken to mean he taken over. He hadn’t. Any power transfer would have been to VP Bush (I don’t recall if that was done.) Plus, the Secretary of State is fourth in line after the VP, the Speaker of the House, and the Sentate President Pro Tempore.
I am not aware of any instance where a Secretary of State was in command due to succession. There have been several people who once served as Secretary that were elected as President, but none have succeeded to the office besides the Vice-President. Haig stated he was in charge while the VP traveled, but that overlooked the Speaker of the House and the President Pro Tempore of the Senate. I think Haig meant to say, “I’m answering the phones.”
Haig was widely criticized for his claim, although I don't think he was actually claiming he was "in charge of the country".
The line of succession was changed by Harry Truman in 1945, a couple of months after he succeeded FDR. He inserted the Speaker of the House and Pres of the Senate in front of the cabinet members, and congress approved it. And it was also about that time, I think, that the Secretary of War became the Secretary of Defense (kind of a weasel-wording of the same office).
Thomas Jefferson, but he had to run for and win it years after serving in that post during the first three years of Washington’s administration (trick answer). The order of presidential succession has never gotten past Vice President and into the realms of Speaker of the House or Secretary of State. John Quincy Adams is another, I think, who became president after previously serving as Sec. of State.
When John Wilkes Booth assassinated Lincoln, Secretary of War Edwin Stanton stepped in, took over, made the decisions and gave the orders until Vice President Andrew Johnson could be sworn in. That could have made him “acting” president, if only for a short time.