If you’re part of the 45-to-60ish crowd, chances are you grew up watching — and singing along to — “Schoolhouse Rock.” The Saturday morning education series began airing in 1973 and was originally developed to help kids with math before expanding to other core subjects such as grammar and science. The three-minute vignettes earned a Grammy nomination and were embraced by educators as a supplemental learning tool. In celebration of America’s 200th birthday in 1976, the creative force behind “Rock” decided to focus on U.S. history and began its third season with the episode and song “No More Kings”: The...