The following text from Aviation Week is not unique to the aircraft pictured:
03/07/1960. As-of December 31, 1959, the DC-3 was the second most-used US aircraft in air transportation, with 305 aircraft used by US airlines. North Central Airlines had the largest fleet with 32 aircraft.
05/02/1960. In 1949 there were 449 DC-3s in service with US Scheduled Airlines.