After the development of Sun Valley by the Union Pacific Railroad in 1936, Ketchum became popular with celebrities, including Gary Cooper and Ernest Hemingway. Hemingway loved the surrounding area; he fished, hunted, and in the late 1950s bought a home overlooking the Wood River in nearby Warm Springs. It was there he committed suicide; he and his granddaughter, model and actress Margaux Hemingway, are buried in the Ketchum Cemetery. The local elementary school is named in his honor.
Every Labor Day weekend, Ketchum hosts the Wagon Days festival, a themed carnival featuring Old West wagon trains, narrow ore wagons, a parade, and simulated street gunfights.
The Clint Eastwood film Pale Rider (1985) was partially filmed in Sawtooth Mountains nearby Ketchum.