The band found their greatest success in the late 1960s and early 1970s, under the leadership of singer/keyboardist Burton Cummings and guitarist Randy Bachman, with hit songs including "American Woman", "These Eyes", and "No Time".

[8][9] They then signed with Quality Records and released several singles in 1963–64, which gained some regional notice around Winnipeg but made little impact in the rest of Canada.

[12] That album's single, "Shakin' All Over", earlier recorded by Johnny Kidd & the Pirates, was the band's first major hit, reaching no.

[13][14] Their Canadian label, Quality Records, disguised the single by crediting it to Guess Who?, as a publicity stunt to generate speculation that it was by a more famous British Invasion band working incognito.

[17] The Guess Who released its first album, It's Time, with Cummings on vocals and keyboards, Bachman on guitar, Kale on bass, and Peterson on drums,[14] in the summer of 1966.

[19][20] The band travelled to the United Kingdom to promote the single, but this was a financial mistake as the song quickly dropped off the charts.

[25] Richardson signed the Guess Who to his Nimbus 9 label and production company, and personally financed the recording of a new album in late 1968.

This made The Guess Who the first Canadian band to achieve a chart-topping single in the United States during the Billboard Hot 100 era.

[33] While American Woman became a success in the early months of 1970, Bachman recorded an all-instrumental solo album titled Axe with Peterson on drums.

)[41] Bachman then took a break from touring with The Guess Who due to illness, with American guitarist Bobby Sabellico filling in temporarily.

On July 17, 1970, the band was invited to perform at the White House for US President Richard Nixon's family and guests, but they were asked not to play "American Woman" due to its apparent criticism of the United States.

[45] The expanded lineup quickly recorded the album Share the Land, which was released in late 1970 and became another substantial hit in both Canada and the United States.

[46] The band's commercial fortunes and chart performance then declined in the United States, perhaps due to an inability to be taken seriously by the fans of album rock radio,[47] though they remained very successful in their native Canada.

[50][17] Leskiw was replaced on short notice by guitarist/singer Donnie McDougall, a veteran of the Winnipeg rock scene who had most recently played with the Vancouver-based Mother Tucker's Yellow Duck.

[55] The Guess Who replaced Kale with Bill Wallace, who had played with Kurt Winter in their early Winnipeg band Brother.

[44] They were replaced by a single guitarist, Domenic Troiano, who had founded the successful Canadian band Bush[59] and had also served briefly with James Gang.

[62] Due to Troiano's songwriting influence, these albums moved toward Jazz Rock; Cummings was unhappy with the stylistic change and the group broke up and disbanded in October 1975.

In 1976, Peterson linked up with Toronto singer and ex-Domenic Troiano associate Roy Kenner and American guitarist Bobby Sabellico in an R&B band, Delphia, which went unsigned and left no recordings.

[71] Members of the classic-era Guess Who reunited a number of times over the years, the first being when Cummings, Bachman, Peterson, and late-classic-era bassist Wallace reformed for a CBC television special in November 1979.

[74] In May 1997, with their hometown of Winnipeg facing severe floods, Cummings and Bachman reunited for a fundraiser for disaster relief, organized by Canadian actor Tom Jackson.

[75] At the request of the Premier of Manitoba, Cummings, Bachman, Kale, and Peterson appeared together at the closing ceremonies of the Pan American Games at Winnipeg Stadium on August 8, 1999.

Another lineup featuring classic-era members Cummings, Bachman, Peterson, McDougall, and Wallace engaged in a lengthy reunion tour from 2000 to 2003, including playing the halftime show at the 2000 Grey Cup.

[77] On July 30, 2003, this lineup performed before an estimated audience of 450,000 at the Molson Canadian Rocks for Toronto SARS benefit concert.

Kale used his newly registered mark to start a new band in the United States, hiring a variety of musicians whom he called "The Guess Who.

[86][87] Early in 2023, Bachman and Cummings sent multiple cease-and-desist letters to the Peterson-led nostalgia band, accusing them of misleading the public.

Following this action, the cover band was unable to perform most of the group's biggest hits, including "These Eyes", "American Woman", "No Time", and "Share The Land", and many others.

[5] The Guess Who's original members, Cummings, Bachman, Kale and Peterson, were inducted into the Canadian Music Hall of Fame in 1987.

[93][94] The signatures of then-current band members Bachman, Cummings, McDougall, Peterson, and Wallace are engraved into the commemorative stone.

[95] In 2018, a number of master tapes of the band's recordings, possibly including unreleased material, were donated to the St. Vital Museum in Winnipeg.