The DC-3 actually started with the DC-1
prototype, which also has an interesting story but that is for another node.
The DC-3 started out as the DST or Douglas Sleeper Transport. Only a few of these aircraft exist today. You can spot a DST by the second row of small windows in the fuselage
above the "normal" windows. The DST had a row of bunks above the seats, allowing passengers to rest during long flights, each bunk had a small window so the passenger could see out if s/he chose to. There was almost no demand for the DST so Douglas
removed the bunks from the design and installed a shelf for hats. Most airlines would not allow carry-on luggage
More DC-3s have been produced than any other airliner in the world. Despite the high production of these aircraft not one has ever suffered a documented structural failure of any kind. This is due to the zealous over-engineering of Douglas and his team. This has given the DC-3 the reputation (and rightfully so) of being the safest aircraft ever built. A series of tall-tales arouse among pilots about the versatility of the DC-3, most of them being true. One such story was of a pilot who encountered severe wind sheer so bad that his altitude fluctuated between 1,000 feet and 13,000 feet. The turbulence was so bad that the seats were ripped from the floor of the aircraft. Upon landing the mechanics went over the plane with a fine-tooth comb looking for damage. The inspection resulted in drilling new holes in the floor, bolting the seats down and flying on to the destination.
Shortly after the introduction and rise in popularity of the DC-3 a race was staged from England to The Cape of Good Hope. There were four entries, a Boeing 247, three identical aircraft specially built for the race and an Imperial Airways DC-3. Each plane was required to make no fewer than three stops along the route. However, Imperial Airways announced that their standard DC-3 would fly it's normal route (over 1,500 miles out of the way) and with a full load of passengers and cargo making about 16 stops along the way. The Imperial Airways DC-3 finished a close second, only hours behind one of the custom racers.
Delta employees recently located a DC-3 first sold to the airline in 1940 for air mail and passenger service. This ship was in Costa Rica hauling freight. The aircraft had been in service non-stop since it rolled off the assembly line in 1940, it had logged so many hours in the air they added up to a total of ten years of non-stop flight.
The ship was bought and flown back to the US for an extensive restoration, it now tours major Delta hubs as a flying museum for Delta employees and their families.
I was able to see the aircraft (despite not working for Delta) and go aboard. The entire plane is covered in mirror-finished aluminum. All the fabrics for the interior had to be custom woven and dyed. To date this is the most extensive DC-3 restoration ever. If you would like photos of the aircraft in color or black & white email or msg me. I shot two rolls of film in under an hour.
Apendix: gn0sis has reminded me that there were almost 5,000 DC 3s build by the Russians under the names Li-2 and Ps-84. Thanks gn0sis.