Los Angeles Airways Flight 841 was a Sikorsky S-61L helicopter that crashed at 5:50 p.m. on May 22, 1968 in the city of Paramount, California. All twenty passengers and three crewmembers were killed. At the time, it was the worst helicopter-related accident in U.S. aviation history.
Events - Fires, Crashes, and Disasters, Vehicle Accidents
Links: en.wikipedia.org, aviation-safety.net, www.planecrashinfo.com, www.thisdayinaviation.com