J. P. Morgan monitored his competition by placing officers of his bank on the boards of companies that he wanted to control. This method was known as a (n)

This method was known as an interlocking directorate.

Explanation:

Interlocking directorate is the practice of the same individual being a member of multiple boards in companies.

In this case, J. P. Morgan has placed officers from his bank onto other companies' boards, thus carrying out the interlocking directorate method.