Grant Wood American Gothic, 1930, Art Institute of Chicago
http://www.pbs.org/wgbh/sisterwendy/works/ame.html
Meaning: could be one of two things: it could be seen as a celebration of "American" values - decent, hardworking Christian citizens - or else a satiric critique of the selfsame thing. The pair's dour expressions led many outside the Midwest to believe that Wood, a self-proclaimed Regionalist, was poking fun at rural life.
Elements helping to portray the meaning of their hardworking lives (no fun here) are their forbidding expressions, simiple clothes and the pitch fork in the man's hand (the local dentist and his sister were models for the painting) suggesting that his work is what is important to him. The frontal positioning of the figures also makes the message more forceful.
Another painting with a strong message - this time of the loneliness of city life at night. The few figures, not communicating seated at the bar: is Edward Hopper's Night Hawk 1942
http://en.wikipedia.org/wiki/Nighthawks
Check it out and you will see that the light is important feature. All around the bar is darkness. The contrast is stark and even scary.