"O Brother, Where Art Thou?" is loosely based on Homer's epic poem, "The Odyssey." Like the hero Odysseus (or Ulysses) in the poem, the three main characters in the Coen brothers movie -- Ulysses Everett McGill, Pete Hogwallop and Delmar O'Donnell -- set out on a long journey fraught with obstacles.
The three travelers' quest is a supposed treasure ($1.2 million in stolen cash) that McGill claims to have buried outside his Mississippi home, soon due to be flooded to build a dam for electricity generation. Much of the story explores the Old South-vs.-New-South theme, with "old-timey" bank robbers, KKK cross-burnings, chain gangs, lynch mobs and Depression Era poverty giving way to a "brave new world."
Ulysses Everett McGill (George Clooney) describes the transition near the end of the movie, as he and his companions begin swimming to safety after the Mississippi valley -- and his home -- are flooded to make way for the dam:
"No, the fact is, they're flooding this valley so they can hydroelectric up the whole durn state. Yes, sir, the South is gonna change. Everything's gonna be put on electricity and run on a paying basis. Out with the old spiritual mumbo jumbo, the superstitions, and the backward ways. We're gonna see a brave new world where they run everybody a wire and hook us all up to a grid. Yes, sir, a veritable age of reason. Like the one they had in France. Not a moment too soon."
While this speech touches on the environmental changes to come (re-engineering the natural world to suit human needs -- in this case, flooding a valley to produce electricity), the prevailing theme of the movie is the South's changing cultural environment. McGill and his companions explore their world in 1930, just as momentous changes are beginning to take place. Many of the cultural hallmarks they encounter will gradually fade away, including:
- Grinding poverty, which will ease as the Depression ends and the military-industrial buildup World War II begins
- The KKK and lynch mobs -- not necessarily eliminated, but increasingly driven into the shadows as racial attitudes evolve and the civil rights era draws near
- Rough, rural living and living "on the road" -- soon to be swept away by electrified cities and homes, paved roads and interstate highways
- Travel by foot and train -- increasingly replaced by car travel
- Things like cotton houses, carrying blocks of ice down dirt roads while barefooted (as ice-boxes are replaced by refrigerators), lawlessness (both by "justice"-dispensing marshalls and outlaws like George "Babyface" Nelson), anti-miscegenation (mingling of races) beliefs and superstitions (belief in sirens, the devil, men turned into toads, etc.)