The Board supervise approximately 900 state member banks and 5,000 bank holding companies.

http://en.wikipedia.org/wiki/Federal_Reserve_System

The Board and, under delegated authority, the Federal Reserve Banks, supervise approximately 900 state member banks and 5,000 bank holding companies. Other federal agencies also serve as the primary federal supervisors of commercial banks; the Office of the Comptroller of the Currency supervises national banks, and the Federal Deposit Insurance Corporation supervises state banks that are not members of the Federal Reserve System.