Chicago Blues grew out of the more classic Delta blues in the 1940s after millions of African-Americans left the southern United States in what was termed the Great Migration. At the time, the South was still plagued by intense racial segregation and discrimination. Many of those African-Americans ended up in cities in the northeast, midwest and west.

The Chicago Blues sound was developed by blues musicians who settled in Chicago, and became popular during the 1950s and 1960s. It was really the foundation for rock and roll and modern electric blues.

The unique sound developed in Chicago differed from the earlier classic Delta style blues in that it had a more gritty, urban feel. It was defined by the use of the electric guitars, amplified harps (harmonicas), electric bass, piano, and occasionally other instruments like saxophone. It used loud and often overdriven amplifiers. In contrast, the earlier classic or Delta style blues was acoustic in nature.

The lyrics of the Chicago sound also tended to reflect the struggles of life in the city as opposed to life in the country.