Castleberry & Associates PC. Because we care!! For more than 15 years, Castleberry & Associates PC has served as a trusted business partner to clients throughout the Norman Oklahoma area. Established in 1994 by Robert M. Castleberry, we've been providing services to individuals and to businesses of all sizes. Your success is our success, and all of us here at Castleberry & Associates PC look forward to working together with you to achieving the bright financial future you deserve!