Sister Mary Jean Ryan has stepped down as president of SSM Health Care and will become chair of the hospital system's board of directors. She has been the company's CEO since its founding in 1986. William Thompson, 60, will follow Ryan as the company's CEO. SSM, which is based in St. Louis, owns 15 hospitals and two nursing homes in Missouri, Illinois, Wisconsin, and Oklahoma. Thompson has worked for SSM for 31 years, and became COO in 2009.