When the Mississippi-born singer and guitarist known as Muddy Waters (born McKinley Morganfield) moved to Chicago in 1943 with his “bottleneck” guitar style, he was poised to play a major role in bringing southern blues into the popular music mainstream. He had already been discovered and recorded by Alan Lomax for the Library of Congress’s folksong archive, but Chicago’s urban clubs offered new opportunities. Waters changed to the electric guitar, formed a band, and began issuing a series of increasingly popular and influential records. Touring in the United States and internationally, he was eventually embraced by new, younger audiences. This poster advertises the Muddy Water Blues Band’s appearance at San Francisco’s famous rock venue, the Fillmore Auditorium, in 1966. Although pertinent information about the event was difficult to decipher, designer Wes Wilson’s swelling letters proved influential, helping to launch a craze for collecting psychedelic posters.