Bluegrass evolved from "mountain music," the indigenous music of the people of Appalachia, jug bands, and 19th- and early 20th-century string band styles. Bluegrass fully evolved in the late 1930s or early 1940s with the music of Bill Monroe.
The name of the music has two sources; the nickname of Kentucky, the Bluegrass state, and the name of Bill Monroe's band, "The Blue Grass Boys." It was not until the 1950s that this style of music was widely called bluegrass.
Bluegrass is played on acoustic stringed instruments with vocals. The main instruments are (but not limited to) banjo, acoustic guitar, violin, mandolin, acoustic bass and resonator guitar. Bluegrass style often involves lightning-fast fingerpicking.
There are many famous bluegrass musicians. The most famous, and most important to the genre, has to be Bill Monroe (1911-1996), who gave birth to the genre. The second most important name in bluegrass is arguably Earl Scruggs (b.1924) who, along with his partner Lester Flatt (1914-1979), played a major role in popularizing bluegrass. Earl Scruggs invented the three-finger picking style for the banjo that is one of the hallmarks of the music.
The soundtrack to the 2000 movie, "O Brother Where Art Thou?" gave bluegrass music new exposure. This album, filled with bluegrass and other roots music, went multiplatinum and won numerous awards, including a Grammy for Album of the Year in 2002.