What is the longest continuously running American series (all genres) of all time?

1. “American” means originating in the United States of America—shows that are aired in the U.S.A. but that did not originate there are not included.
2. “Series” means any television show designed to have multiple-episodes over time.
3. “Continuously running,” for the purpose of this question, means without ceasing and over time (i.e.--not a ranking by number of episodes).