The Open classification was created in 1952 to help the Pacific Coast League build itself into a major league. It was considered to be a notch above AAA but in assessing talent level, it does not appear to have been any higher. The PCL was only circuit to carry the designation. After the National League moved into Los Angeles and San Francisco in 1958, the major league hopes of the league died and it returned to AAA. The Open classification was abolished in the same year.
- average paid attendance of at least 2,250,000 for the five seasons preceding the application
- total population of the member cities of at least 10,000,000
- combined park capacity of at least 125,000
- average paid attendance of at least 3,500,000 for the previous three seasons
- total population of the member cities of at least 15,000,000
- each park had to have a capacity of at least 25,000
- the league had to consist of at least eight teams playing a balanced schedule of at least 154 games