Born in the smoky halls of turn-of-the-century vaudeville and thrust into mainstream American culture by the advent of radio and television, stand-up comedy is the entertainment industry's most accurate social thermometer. From Milton Berle to Roseanne Barr, comics have used the power of laughter to challenge Americans to face the controversial issues of the day, whether sex, government or religion. A good routine can turn the most tragic headlines into a gut-wrenching guffaw. Sometimes comics go too far for a laugh; sometimes they're the only ones brave enough to point out hypocrisy and social injustice.

Stand-up comedian Jerry Seinfeld

The profession developed long before the discovery of electricity. Court jesters performed the first stand-up routines in medieval times. Elements of stand-up also pervaded William Shakespeare's work in the form of a fool providing the audience with a dose of comic relief. If the nineteenth-century American humorist...