Three hundred thirty-one episodes. One hundred twenty-four Emmy nominations. Forty-nine million viewers. One George Clooney.

Thirty years ago, ER debuted on NBC, introducing viewers to the emergency room doctors at County General Hospital in Chicago. The medical drama would launch the careers of Clooney, Noah Wyle and Julianna Margulies and run for 15 seasons, making it the second longest running medical drama in TV history.