BOK Financial Corporation is a financial holding company that is primarily engaged in banking and bank-related activities through Bank of Oklahoma, N.A. (BOk), Bank of Texas, N.A., Bank of Albuquerque N.A. and Bank of Arkansas, N.A. Other significant operating subsidiaries include BOSC, Inc., which is a full-service securities firm with specialized expertise in public and municipal finance and private placements. In October 2002, Bank of Texas acquired Houston-based Bank of Tanglewood, expanding Bank of Texas to 12 locations in the Greater Houston area.