How many treasurers are there in the U.S.?

Question

My friend and i saw different names on a couple 100 dollar bills made in the same year.

Answer 1

When the Treasurer of the United States changes, the series year doesn't change, but they do add a letter to the series designation. For example, the only difference between Series 2004 and Series 2004 A $100 banknotes is the treasurer's signature (Series 2004: Rosario Marin, Series 2004 A: Anna Escobedo Cabral)
The series year changes when the design of the banknote changes or when the Secretary of the Treasury changes (for example, Series 2004/2004A notes are signed by John A. Snow as Secretary. Series 2006 notes are signed by Henry Paulsen as Secretary.)

Answer 2

I think you mean US Mints. The US mint has facilities at:
United States Mint Headquarters, Washington, D.C.
United States Mint at Philadelphia, Pennsylvania
United States Mint at Denver, Colorado
United States Mint at San Francisco, California
United States Mint at West Point, New York
United States Bullion Depository, Fort Knox, Kentucky