It was a Sunday afternoon at the South Omaha Eagles Hall, a Czech stronghold in an increasingly Hispanic neighborhood here. Under a low ceiling and fluorescent lights, Lila Dvorak, 74, danced a two-step polka to the music of a three-piece combo.

Dvorak is Czech-American, and a child of the Great Depression, like almost all of the 150 or so people present. She is a regular at the dances and wore a fancy magenta dress for the occasion. "Polka people are happier people," she said. "I don't think you see anyone around here with a long face."

All over the United States, where there are Eastern Europeans, there is polka. In the isolated farmland counties of eastern Nebraska, where it is not uncommon to drive 30 miles for groceries, polka helps tie people together. The dances and the radio shows devoted to the music keep old friends in touch and circulate local news.

Brought to the United States by Central European immigrants in the mid-19th century, polka is now part of American vernacular culture, a music with little commercial viability but a strong social function. From state to state, its details and dance steps carry codes of Old World origin and New World region....