In 1974, Michael Crichton wrote a screenplay about his own experiences as a physician in a hospital emergency room. The screenplay was unsuccessful so Crichton decided to focus on other topics. In 1993 he began collaborating with director Steven Spielberg on the film adaptation of the book Jurassic Park. Crichton and Spielberg then turned to ER, but decided to make it a two-hour pilot for a television series instead of a feature film. The script used to shoot the pilot was virtually unchanged from what Crichton had written in 1974.
After Spielberg had joined as a producer, NBC ordered six episodes. ER’s success surprised the networks and critics alike, and therefore NBC continued to broadcast the show. Spielberg left the show after one year, while Crichton remained executive producer until his death in November 2008.