Letter from Alfred Stille to Isaac Hays, Cincinnati, Ohio, May 7, 1850 A two and three-quarter page letter written by Dr. Alfred Stille to Dr. Isaac Hays on May 7, 1850, from Cincinnati, Ohio. Stille describes attending the American Medical Association (AMA) convention. This is the first of two letters from Stille chronicling the AMA convention; the AMA was founded in 1847.