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March 26
The Rosses move to 2961 St Antoine Street in the Brewster Projects in Detroit, Michigan on the same day Diana turns 14. They previously lived at 5726 St Antoine Street, before moving to 635 Belmont Avenue in November 1955. After Balch Elementary School, Diana Ross attended Dwyer Junior High School and then Cass Technical High.
Diana sang in the Olivet Baptist church choir during her childhood. 
The Primettes (Florence Ballard, Betty McGlown, Diana Ross, Mary Wilson) are formed as a sister group to the Primes (Paul Williams, Eddie Kendricks and Kell Osborne – Paul and Eddie will later be members of the Temptations). The Primes’ manager, Milton Jenkins, was dating his future wife, Maxine Ballard, elder sister of Florence Ballard, who recommended her. Florence brought her friend Mary Wilson in. Paul was dating Betty McGlown at that time and Eddie recommended Diana Ross. 
The Primettes sang a Ray Charles’ song “(Night Time Is) The Right Time” at their first meeting. Most of the books situate their first meeting in 1959 but according to several interviews and articles, the first meeting of Diana with Mary and Florence occurred in 1958 (for example, in the March 20, 1966 issue of the Chicago Tribune: “The three met and started singing together eight years ago”, so in 1958, or “ ‘We started singing together seven years ago, when we were 14 and 15,’ reported Diane.” in the Star Gazette from Elmira, NY, October 23, 1965 issue, so again in 1958).
Diana Ross about how the group got started: “We all lived in the same neighborhood, although we didn’t know each other. It was really kind of crazy; we went right into rehearsal one day and night and then we had a show to do the next evening. And we’ve been together ever since, singing at record hops and other affairs on weekends while we were still in high school.”
Summer
The Primettes rehearse in a hall on 12th street in Detroit and play some gigs at local clubs like the Gold Coast.
1958
1958 - 59
1959
March 6
March 26 
June 30 
Mary Wilson turns 16. 
Diana Ross turns 16. 
Florence Ballard turns 17. 
July 4
The Primettes are contestant at the amateur talent show during the International Freedom Festival held during the Emancipation Day Celebrations in Windsor (Canada). The Primettes perform “(Night Time Is) The Right Time” and four other songs (probably among those the same songs they sung during their audition at Motown) and win the contest.
July (-)
Diana Ross asks to her almost neighbor William ‘Smokey’ Robinson to get the Primettes an audition at Motown. They first audition before him at his wife Claudette’s family house. Smokey engages the Primettes’ guitarist Marv Tarplin.
July - September
The Primettes’ audition at Motown is attended by Robert Bateman, Richard Morris, Berry Gordy and Janie Bradford.
The Primettes perform “(Night Time Is) The Right Time”, “The Twist”, “There’s Something On My Mind”, “There Goes My Baby” and both Florence and Diana sing leads. Berry asks Diana to re-due “There Goes My Baby” and finally tells the girls to finish high school first and to come back later.
The Primettes go to another label, Lupine (Bob West’s label located at that time on Forest Street in Detroit), and record many background vocals for several artists.
Note: in his autobiography “To Be Loved” p.144-146, Berry Gordy situates this audition approximately six months before he first met Marvin Gaye (which happened during the Motown Christmas party in 1960). This would situate the audition around June or early July which is too close or event before the Windsor contest (July 4), The Supremes audition at Motown might have occurred later in July.
early September
The Primettes record a single (“Tears Of Sorrow” b/w “Pretty Baby”, both songs written by Richard Morris who attended their Motown audition). Diana Ross sing lead on “Tears Of Sorrows” and Mary Wilson on “Pretty Baby”. Richard Morris brought two more female backup singers for “Pretty Baby”. It’s unclear if the single was released at that time (see the discography for more information). 
Betty McGlown announces a few days later that she is getting married (Travis being her married name) and quit the group. Barbara Martin replaces her.
Note: some biographies situates this single in 1959 and even precisely in March 1959 but that’s unlikely correct.
Sept - October
The Primettes go almost every day after school at Motown in hope to get noticed. They finally record handclaps for Marvin Gaye and background vocals for Mabel John. The Primettes also record backup vocals on Mary Wells songs (which went unreleased at that time), Swingin’ Sammy Ward (probably among others).
Florence is raped by a schoolmate and almost quit the group. 
October (-)
Still without a contract with Motown yet, the Primettes record “After All” (one of their first, if not the first song recorded at Motown) and “You Can Depend On Me” (produced by Smokey Robinson).
Recording session for “Who’s Loving You” (see also January-July 1961) and “Play A Sad Song” (see also January 17, 1962).
Oct - December
Recording session for “Too Hot” (version 1 - see also June (-) ) and “You’re Gonna Come To Me” (the first of several very different versions), also recorded June 15, 1961  and August 15, 1961 (see also the discography for more information).
December (-)
Recording session for “I Want A Guy”.
1960
January (-)
Recording session for “Never Again”.
January 15
The group is given a recording contract with Motown Records and its name is changed to “The Supremes”. The contracts are signed by their mothers because all the members of the group are still underage (except Barbara Martin but her mother is there as well).
Note: Most of the sources state the contracts were signed this day, some that they were signed only on January 23. To postpone the signature to January 23 would be curious as they were not authorized to bring unsigned contracts at home.
January - July
Recording sessions for “Who’s Loving You” (see also October 1960), “The Boy That Got Away”, “Hey Baby”, “Because I Love Him”. Probably around that time too, and surely in 1961, the Motown version of “Tears Of Sorrow”.
March 9
Single “I Want A Guy” released (the first few copies are on the Motown label, the Supremes are then quickly switched to the Tamla label).
April (-)
Recording session for “Buttered Popcorn”.  
June (-)
Recording session for “Too Hot” (version 2 - see also Oct-Dec 1960). 
June 3
Recording session for “Baby Don’t Go”, “Too Hot” (4th and last version).
June 15
Recording session for “You’re Gonna Come To Me” (version 1, also recorded around the end of 1960 or the beginning of 1961 according to the booklet of “Meet the Supremes – Expanded”) (this version on “Lost & Found”) - see the discography for more information.
July 21
Single “Buttered Popcorn” released but soon withdrawn to be reissued with an alternate take. 
August 14
Recording session for “He’s Seventeen”, “Save Me A Star”, “Heavenly Father”.
August 15
Recording session for “You’re Gonna Come To Me” (version 2) (erroneously credited as version 1 on “Where did Our Love Go – Expanded”) (see also Oct-March 61).
(-)
The Supremes perform at clubs like the Chit-Chat Lounge and the Roostertail in Detroit, and occasionally out of town for weekend gigs in Cincinnati, Cleveland and Pittsburg (see early 1962). 
September 19
Recording session for “Those DJ Shows”.
December 8
Recording session for “Your Heart Belongs To Me”, “The Tears”.
December 12
Recording session (unknown songs). 
December (-) 
Barbara Martin marries Willie Richardson and stops recording with the group but still participates to gigs.
1961