Opera Company of Philadelphia was created in 1975.
Your answer depends totally on the size of the opera company. Further, it depends on whether the company includes -- or not -- the opera ballet, the opera chorus, the opera orchestra, the opera production company and crew, the administration for the company, and so forth.
Opera Company of Boston ended in 1990.
O'Donoghue's Opera was created in 1965.
The Threepenny opera was created from the Beggars opera in 1728. It was written by John Gay, a well known plat writer. It was created from the Beggars opera.
D'Oyly Carte Opera Company ended in 1982.
Opera a la Carte - UK - was created in 1993.
Opera a la Carte - US - was created in 1970.
Century Opera Company was created in 1913.
Philadelphia Opera Company was created in 1938.
Boston Opera Company was created in 1908.
Canadian Opera Company was created in 1950.
Chicago Opera Company was created in 1940.
Berkshire Opera Company was created in 1962.
Aborn Opera Company was created in 1895.
American Opera Company was created in 1937.
Knoxville Opera Company was created in 1978.