South Dakota Planning Company, LLC (SDPC) is an estate planning and trust advisory firm, founded by Al W. King III and Pierce H. McDowell III, that advises both domestic and international clients. SDPC, a Delaware LLC doing business in New York City, works closely with its sister company, South Dakota Trust Company LLC (SDTC), which is an independent trust company, headquartered in Sioux Falls, South Dakota, specializing in providing trust administration for the wealthy. SDPC and SDTC are wholly owned subsidiaries of Third Constellation, LLC, a Delaware LLC, based in New York City.