Starting with the Cloudster.
Donald W. Douglas started the Douglas Aircraft Company in 1921 by building the Cloudster. He used c/n 100 to pretend he was an experienced aircraft builder. Three years later he was firmly established as being one when his World Cruiser flew around the world. Pre-war Douglas built a large number of aircraft for the US military.
On May 11, 1934 the DC-2 made it's first flight and entered service a week later. It was followed by the larger DC-3 which made it's first flight on December 17, 1935. There were 607 civil versions built and 10,048 military C-47's and C-53's. When including the Russian Li-2 and Japanese L2D, the grand total is over 16,000.
The DC-series continued with the DC-4E which flew first on June 7, 1938 but that was no success. Douglas developed a new version, also as DC-4, but production output was taken over by the US War Department as C-54 which made it's first flight on February 14, 1942.
In between the El Segundo Division produced it's only civil airliner, the unsuccessfull DC-5 which made it's first flight February 20, 1939. Only 12 were built.
After the war the DC-series continued with the pressurized DC-6 (first flight February 15, 1946) and the DC-7 (May 18, 1953).
After Boeing announced the 707 Douglas followed soon with the DC-8 which took off on it's maiden flight, only five months later than the 707, on May 30, 1958. The smaller twin-engined DC-9 did it's first flight on February 1965.
Struggling with production rates and financial trouble developing their first wide-body Douglas was forced to merge with McDonnell Aircraft Corporation in 1967. Eventually the DC-10 made it's first flight on August 29, 1970 and went into service August 5 the next year. The DC-9 was further developed into the MD-80 and -90 series and the DC-10 into the MD-11. The prototype of the MD-95-30 was rebranded as the Boeing 717 after McDonnell Douglas was taken over by Boeing on August 1, 1997.