Complex sentence: During the 11th and final season, Thomas decided to retire from the show and the program ended in the spring of 1964, finishing as still one of the most popular television programs and ranking at number nine.
Split into simpler sentences: During the 11th and final season, Thomas decided to retire from the show and the program ended in spring 1964. At this time, it was still one of the most popular television programs, ranking at number nine.