I found this on a DVD set at my public library. It is almost 4 hours of content on two disks. It uses a lot of old photos and film to supplement the script and tell the visual story of the history of the circus in America. Good documentary.
P.T. Barnum was arguably the main driving force with his eye for the fantastic and how to turn that into shows that would entertain and be profitable. While there came to be many, many smaller circuses touring the big names were Barnum, Bailey, and the five Ringling Brothers. Eventually, as Barnum then Bailey died the remains became all one big circus. At its height the traveling circus was a small city and returned large profits to their owners.
This documentary, the story of the genesis then growth of the circuses, is very well put together, focusing not only on the creators and owners but also on select performers and incidents like the big top fire that killed a large number of audience members who could not escape.
The documentary credits the advent of television as a reason circuses eventually became unprofitable. Citing shows like the Ed Sullivan show, which brought circus type magic into peoples' homes, it was no longer necessary to go to a circus to be amazed. Plus the additional safety restrictions on circus operation and the advent of labor unions demanding higher wages and benefits, all which contributed to the demise of the big circus.