American folk music has its origins in the oral traditions of earlier cultures. It began primarily with Irish and English ballads, but eventually fused with African, Native-American and other musical styles.
When West Africans were brought to America during the time of slavery, they retained their unique musical traditions. Over time, their songs of hardship mixed with European folk style to become a uniquely American art form known as the blues.
During the early 1950s, folk music entered its heyday and acquired much popularity with artists such as Woody Guthrie and Pete Seeger leading the way.
The next decade saw a resurgence of interest in folk music as it figured prominently in social protest. Bob Dylan and the Byrds pioneered the fusion of folk with rock, thus bringing the genre into the mainstream.
Folk music is always changing and has evolved considerably over the decades. Still, it exerts considerable influence over today's popular music even as it continues in its own right.