Fairfield (Ohio) Hospital. Fairfield Hospital, part of Cincinnati-based Mercy Health, has served residents of Butler County and northern Cincinnati for more than three decades. Last year, iVantage named Fairfield a HealthStrong Top 100 Hospital. In 2016, Healthgrades named the hospital among the 100 best in the nation for cardiac care, gastrointestinal care, general surgery and pulmonary care.