Blues developed primarily in the Southern US region (i.e. Mississippi Delta region and later into the Memphis, Chicago and New Orleans regions). After the freeing of slaves in the late 19th and 20th centuries, African music traditions had a larger reciprocal influence as (some) African-Americans, now free from slavery, became travelling musicians and began influencing other African-American musicians. Within their travels, they seeded new musical ideas of vocal and lyrical utterances and improvisation, driving rhythmic patterns and an overall unique communication style that propagated throughout the South and then throughout the northern areas. Cross-pollination of musical influences continued and the freedom of African-American slaves provided more thematic content t to (i.e. white American culture) to the Blues. Continuation of oral traditions proliferated among the illiterate African-American Delta area of the south. Bluesmen such as Muddy Waters, and Robert Johnson became iconic figures holding fast to tradition and form while making history for their lyrically poignant, simple guitar-stylings and overall individualized sound.
Blues songs filled with non-subtle descriptions of relationships, love, religion, work and life continued to permeate repetitive call and response lyrics in reflective style to African poetry and song forms. Musicologist Ray Pratt aptly suggests that the use of metaphors and creative word-smithing mirror distant sounds of traditionally implied rhythms and elusive non-exact pitches. Continuing with its African influence, many early 20th century African-American musicians, such as Sid Hemphill (“The Sidewalks of New York”) from the Mississippi area, incorporated various musical styles and instruments to increase their performance abilities. During this musical transition, various forms, i.e. twelve and eight-bar song form, black ballads and jump-ups, were explored. However, the more common styles, such as twelve bar form and jump-ups resulted in continued use.
As the traditions of the blues spread, various forms of blues styles began to emerge during the early 1900s: Mississippi Delta blues, Southeastern blues, Louisiana blues and East Texas blues. In general, each of the styles held an emphasis on distinct musical interpretations and rhythms (i.e. aggressive or non-aggressive rhythms).
 Ray Pratt, “The Blues: A Discourse of Resistance“ in Rebel Musics: Human Rights, Resistant Sounds, and the Politics of Music Making (Ontario: Black Rose Books, 2003), 128.