This Day in History: 1939-11-27

St. Louis Smog Episode A winter temperature inversion trapped emissions from home and factory coal fires in St. Louis on this day in 1939. Like many other smog episodes, lamps are needed at mid-day because the smog is so thick that sunlight doesn’t penetrate. Investigations and editorials about the smog episode win the St. Louis Post Dispatch a Pulitzer Prize in 1941.