I see the closure of the C-17 line as the end of Douglas heritage.
Thus he left the company in 1920 to move to Los Angeles where he first set Davis-Douglas Co.
You can read about the life of Donald Douglas in the Wikipedia article, at Boeing site or better, in this excerpt from an issue of DC-3.
Hundreds of civil aircraft were produced, over 10,000 military versions.
The military version C-47 Skytrain came to be one of the iconic aircraft of the World War II first and later of the Berlin Airlift (see this post I wrote about our visit to the Berlin Tempelhof Airport, where today a DC-4 is displayed).
In October the Senate approved $2.5 billion in the 2010 budget for 10 more C-17s, which would bring the fleet to 215.