Former Merck and Company executive John Horan has died at the age of 90. He served as Chairman and Chief Executive Officer from 1976 to 1985 and remained on the board of directors until 1993. Merck grew into one of the world’s largest pharmaceutical companies under his watch. He is survived by his wife of 66 years, Julia Fitzgerald, four children, nine grandchildren and two great grandchildren. With two campuses in Upper Gwynedd, Merck is Montgomery County’s largest employer.