Just One according to Wikipedia
Only one aircraft was produced, the prototype and test model. It made its maiden flight on July 1, 1933 and was given the model name Douglas DC-1. During a half year of testing, it performed more than 200 test flights and demonstrated its superiority versus the most used airliners at that time, the Ford Trimotor and Fokker Trimotor. It was flown across the United States, making the journey in a record time of 13 hours, 5 minutes.
TWA accepted the model with a few modifications (mainly increasing seating to 14 passengers and adding more powerful engines) and ordered 20 aircraft. The production model was called the Douglas DC-2.
The DC-1 was sold to Lord Forbes in the United Kingdom in 1938, who operated it for a few months before selling it in France. It was then sold to L�neas A�reas Postales Espa�olas (L.A.P.E.) in Spain in 1938. Later operated by Iberia with the name Negron it crashed at Malaga, Spain in December 1940 and was damaged beyond repair.