This is a Significant Operational milestone.
This was a scheduled air mail service operated by Los Angeles Airways, using Sikorsky S-51's. The service was known by the designation AM-84. Passenger services started a few years later.
Source: "Los Angeles Airways - The World's First Scheduled Helicopter Airline", Clarence M. Bellinn, Journal of the American Helicopter Society, Vol. 1,No. 1, January 1956, Page 111