Wilson had a stroke and was too sick to be president for nearly half his term.
His wife, Edith, took over and ran the country during this period. Back then there were no provision for temporary power transfer if the president was incapacitated. The VP could only assume power if the president died, so Edith was the first female president.
That was Edith, his second wife, whom Wilson met and married in 1915. Edith had a distinguished genealogy, being a descendant of Pocohantas and related to Thomas Jefferson and Martha Washington.
Wilson had the stroke in October 1919 and she effectively was President until March of 1921.
My 4th grade teacher knew Edith Wilson and arranged to have her come speak to us, but she became ill and wasn’t able to follow through. She died later that year.