Editing Stephen Stills (section)

=== Crosby, Stills, Nash & Young (1969–1970) ===
{{main article|Crosby, Stills, Nash & Young}}
In late 1968, Stills joined forces with David Crosby (late of The [[Byrds]]) and Graham Nash (late of [[The Hollies]]) to form [[Crosby, Stills, Nash & Young|Crosby, Stills & Nash]]. Several of Stills's songs on the group's [[Crosby, Stills & Nash (album)|debut album]], including "[[Suite: Judy Blue Eyes]]" and "You Don't Have to Cry", were inspired by his on-again off-again relationship with singer [[Judy Collins]]. The album reached No. 6 on the US charts and was certified quadruple platinum.

Stills dominated the recording of the album. Crosby and Nash played guitar on their own songs respectively, while drummer [[Dallas Taylor (drummer)|Dallas Taylor]] played on four tracks and drummer [[Jim Gordon (musician)|Jim Gordon]] on a fifth. Stills played all the bass, organ, and lead guitar parts, as well as acoustic guitar on his own songs. "The other guys won't be offended when I say that one was my baby, and I kind of had the tracks in my head", Stills said.<ref name=":2" />[[File:Crosby Stills Nash and Young 1970.JPG|thumb|right|Crosby Stills Nash and Young 1970]]

Wanting to tour and needing additional musicians to fill out their sound, the band invited former Buffalo Springfield member Neil Young to join them for their first tour and second album to make the group the quartet Crosby, Stills, Nash & Young (initialized as CSN&Y). The first tour started in August 1969 and finished in January 1970, followed by the recording their debut album as a quartet, ''[[Déjà Vu (Crosby, Stills, Nash & Young album)|Déjà Vu]]'' (1970). The foursome quarrelled frequently throughout the recording sessions, in particular Stills and Young, who both fought for control. Stills composed the songs "[[Carry On (Crosby, Stills, Nash & Young song)|Carry On]]" and "[[4 + 20]]" and co-wrote "Everybody I Love You" with Young. He also brought his version of Joni Mitchell's song "Woodstock" for the band to cover. The album reached No. 1 on the US charts and was certified 7 times platinum there, selling over 8 million copies.

In May 1970, CSN&Y recorded Young's "[[Ohio (CSNY song)|Ohio]]" following the [[Kent State massacre]] on May 4. The single's B-side was Stills's "Find the Cost Of Freedom". The single was rush-released by Atlantic Records at the same subsequent time as the group's "Teach Your Children" was climbing the charts. After an extended second tour finishing in July 1970, the band split up acrimoniously. Stills moved to England and started recording his debut solo album.

In April 1971, CSN&Y released ''[[4 Way Street]]'', a double live album recorded in 1970. The album reached No. 1 in 1971 on the US charts and was certified quadruple platinum in the US.

Having played at the [[Monterey Pop Festival]] with Buffalo Springfield and both [[Woodstock Festival|Woodstock]] and [[Altamont Free Concert|Altamont]] with CSN&Y, Stills (along with Crosby) performed at three of the most iconic U.S. rock festivals of the 1960s. During CSN&Y's set at [[Altamont Free Concert]], Stills was reported to have been repeatedly stabbed in the leg by a "stoned-out" Hells Angel, with a sharpened bicycle spoke.<ref>{{Cite web|url=https://www.houstonpress.com/music/inside-altamont-new-book-looks-back-at-rocks-darkest-day-8690359|title=Inside Altamont: New Book Looks Back at Rock's "Darkest Day"|last=Ruggiero|first=Bob|date=2016-08-24|website=Houston Press|access-date=2019-09-20}}</ref> At the band's request, their performance was not included in the subsequent film ''[[Gimme Shelter (1970 film)|Gimme Shelter]]'' (1970).