It’s possible to search for circus and carnival performers/workers in the 1940 U.S. population census.
On the Ancestry Library Edition (Ancestry LE) landing page you will find a list of available U.S. population schedules in the lower right corner. Select 1940, and you will be presented with a search screen. Try the following searches:
Occupation: acrobat (Exact)—291 hits
Occupation: animal trainer (Exact)—68 hits
Occupation: carnival (Exact)—251 hits
Occupation: circus (Exact)—194 hits
Occupation: clown (Exact)—101 hits
Occupation: juggler (Exact)—50 hits
Occupation: magician (Exact)—207 hits
Occupation: tight rope (Exact)—2 hits
Occupation: trapeze (Exact)—194 hits
You can use Ancestry LE at Central Library or any of our branches.