These images were taken between 1938 and 1944 by photographers from the US government's Farm Security Administration (FSA) and Office of War Information (OWI). They were intended as documents are typical American life, concentrating on rural areas. However, as World War II loomed large for the States the photographs took on the distinct tone of propaganda, shifting toward factories full of primped and posed men women Working Hard to Defeat Hitler. Regardless of their uses at the time, these gorgeous photos are a rare colour glimpse at America of the period.
High resolution digital scans are available for free use here. Thanks to Rick Prelinger for the tip.
EDIT: The Huffingpost Post is totally ripping me off.