I found this information about B1 visa applications.
•If you are employed and applying for the business visa sponsored by your employer/company - A letter from employer requesting the Visa for the applicant
addressed to consulate, indicating the purpose and length of the trip as well as the company's/ firm's intent to bear the costs of the entire trip, including lodging , food, medical and other expenses.
USA Business Visa, B1 Visa Information
I would just address it to whom it may concern....there wouldn't be a specific persons name to put on it.
