1920s

Horton was born in Horn Lake, Mississippi. He claimed to be born in 1917, but his birth date is often cited as April 6, 1918. Various sources give the year as 1917 or 1921, although it is most likely he was born in 1921.^[8][6] He was playing the harmonica by the time he was five years old^[5][9] when his father gave him a harmonica as a gift.^[3] Horton dropped out of school at the age of seven.^[6] In his early teens, he lived in Memphis, Tennessee after moving there with his parents.^[3] He claimed that his earliest recordings were done there in the late 1920s with the Memphis Jug Band,^[3] but there is no documentation of them, and he would have been around six years old at the time of the recording sessions that took place in 1926, so this was likely fabricated by Horton.^[8][10]

1930s

In the 1930s he played with numerous blues performers in the Mississippi Delta region.^[5] Horton had already started playing on the streets for tips and the like. Johnny Shines, a childhood friend of Horton's, said, 'I met Walter, really, in 1930, and he would be sitting on the porch, blowing in tin cans, you know, and he'd get sounds out of those things'.^[11] Horton likely spent a short period of time in Chicago in 1938.^[12] It is generally accepted that he was first recorded in Memphis, backing the guitarist Little Buddy Doyle on Doyle's recordings for Okeh Records and Vocalion Records in 1939.^[3][13] These recordings were acoustic duets, in a style popularized by Sleepy John Estes and his harmonicist Hammie Nixon, among others. It can be heard—upon listening to players such as Hammie Nixon—that Horton was heavily influenced by such earlier styles of harmonica playing. On these recordings, Horton's style was not yet fully realized, but there were clear hints of what was to come.

1940s

Horton eventually stopped playing the harmonica for a living, because of poor health^[12] (possibly tuberculosis), and worked mainly outside the music industry in the 1940s.^[3] He worked as a cook, ice man, and undertaker.^[12][11] Walter Horton also met and gave lessons to harp players James Cotton and Little Walter in the 1940s.^[11][14][15] Horton is likely to have developed his musical skills during these times, considering the difference between the styles in his recordings from 1939 and those of the 1950s. Horton had a daughter named 'Christine' in 1945 or 1946 (along with five other children born in unknown years).^[16][17] Walter started playing again in 1948,^[12] and then recording in 1951 and onwards.

1950s

By the early 1950s, Horton was recording again (his first recordings of the decade being in 1951). Horton recorded with Joe Hill Louis in 1951. Horton was invited by Eddie Taylor to join Jimmy Reed's band in 1952, so he moved to Chicago. A couple of weeks after arriving, however, he was invited to join Muddy Waters' blues band when Junior Wells was drafted into the army at the end of 1952. Horton replaced him long enough to record on one session in January 1953.^[3] Horton was fired from the band by the end of 1953, likely due to his drinking and/or unreliability,^[18][3][12] and replaced by Henry 'Pot' Strong.^[19][20] After being fired from the Muddy Waters band, Walter moved back to Memphis and recorded again with Sam Phillips at Sun studios. Horton was among the first to be recorded by Sam Phillips, at Sun Records in Memphis. For his recordings for Sun, Horton was accompanied by the young pianist Phineas Newborn, Jr., who later was a well-known jazz pianist. Horton's instrumental track "Easy", recorded around this time, was based on Ivory Joe Hunter's "I Almost Lost My Mind".^[21][22] During the early 1950s he appeared on the Chicago blues scene, frequently playing with Memphis and Delta musicians who had also moved north, including the guitarists Eddie Taylor and Johnny Shines.^[3] Horton went back to Chicago in 1954. In 1956, Horton recorded 'Walking By Myself', with Jimmy Rogers for Chess; some consider his solo in this song the best he ever recorded.^[23]

1960s

Horton was active in the Chicago blues scene during the 1960s, as blues music gained popularity with white audiences. From the early 1960s onward, he recorded and frequently performed as a sideman with Taylor, Shines, Johnny Young, Sunnyland Slim, Willie Dixon and many others.^[3] Horton recorded his first solo album in 1964^[8] as he was mainly known as a backing musician.

In October 1968, whilst touring the U.K., he recorded the album Southern Comfort with the guitarist Martin Stone (previously with Savoy Brown and later a member of Mighty Baby).^[22] In 1969, Walter recorded 'Johnny Shines with Walter Horton', where some of his best third position playing can be heard ('Sneakin' and Hidin' Part 1 and 2'). Along with this, Walter also recorded with Johnny Winter, J. B. Hutto and the Hawks, Koko Taylor, Fleetwood Mac, and J. L. Smith in 1969.

1970s

Horton toured extensively in places such as Germany,^[24] Finland,^[25] and England. He toured usually as a backing musician and, in the 1970s, he performed at blues and folk music festivals in the United States and Europe, frequently with Dixon's Chicago All-Stars. He also performed on recordings by blues and rock stars.

In the late 1970s, if in town, Horton played the Sunday matinees at B.L.U.E.S, with Homesick James and Floyd Jones,(who had switched from guitar to bass), and he toured the United States with Homesick James Williamson, Guido Sinclair, Eddie Taylor, Richard Molina, Bradley Pierce Smith and Paul Nebenzahl, and he performed on National Public Radio broadcasts. Two of the compilation albums of his work are Mouth-Harp Maestro and Fine Cuts. Also notable is the album Big Walter Horton with Carey Bell, released by Alligator Records in 1972.^[3] He worked at blues festivals and often performed at the Maxwell Street market in Chicago.^[3] In 1977, he played on the Muddy Waters album I'm Ready, produced by Johnny Winter. He also recorded for Blind Pig Records during this period.^[3]

1980s

Horton accompanied John Lee Hooker in the 1980 film The Blues Brothers.^[3] Although in the film his playing is actually overdubbed by Joe Berson as Horton was reportedly undone by the tedious cinematic process of multiple takes and abandoned the set.^[26] His final recordings were made in 1980.^[22] Horton died of heart failure in Chicago in 1981, at the age of 60,^[3][27] in a neighbor's apartment,^[6] and was buried in Restvale Cemetery, in Alsip, Illinois.^[28] Walter's death certificate also mentioned acute alcoholism.^[7]