Despite being a Quaker, Douglas left the University of Chicago faculty at the US entrance into World War II to enlist. In the War, Douglas was decorated for gallantry and lost the use of one arm.
As a Senator, Douglas was a leading liberal. He fought for civil rights before it was fashionable. He was an advocate for public housing and opposed real estate redlining. A fateful compromise of Douglas' was his acceptance in 1949 of a provision in a public housing bill making it difficult for suburbs to build low-income housing (not that they ever wanted to).
Douglas lost re-election in 1966 to Charles Percy.
Prior to his political career, Douglas helped develop the Cobb-Douglas functional form, often used for production functions in economics.