Mary Wilson, an original member of the Supremes, a Detroit-based vocal trio that topped the charts in the 1960s with a dozen No. 1 hits for the Motown label and who later wrote best-selling memoirs about her experiences in the group, died Feb. 8 at her home in Henderson, Nev. She was 76.

Her publicist, Jay Schwartz, confirmed the death. The cause was not immediately known. Ms. Wilson reportedly had a heart attack more than 10 years ago.

Ms. Wilson, who grew up in a Detroit public housing project, was in her early teens when she joined a vocal group that included Florence Ballard and Diana Ross, the other original members of the Supremes. (A fourth member later left the group.)

First known as the Primettes, after a male singing group called the Primes, they signed in 1961 with Berry Gordy’s Motown Records and changed their name to the Supremes.

They first found little success, but soon they made a musical breakthrough after teaming with songwriters and producers Lamont Dozier and Brian and Eddie Holland.

At first, all three Supremes sang lead vocals, depending on the tune. But with Ross singing the lead on the group’s first No. 1 hit, “Where Did Our Love Go?” in 1964, she became the group’s featured performer. The backing harmonies and counter rhythms sung by Ballard and Ms. Wilson were essential to the group’s sound and to the larger success of Motown.

“Even though we were in the background, we were as much a part of the sound as Diane,” Ms. Wilson told The Washington Post in 1986, using Ross’s original first name. “There was a feeling in it, even if we were just the ‘oohs.’ I was a star in the background.”

During the next few years, Holland-Dozier-Holland wrote a string of No. 1 hits for the Supremes, including “Baby Love,” “Come See About Me,” “Stop! In the Name of Love,” “Back in My Arms Again,” “I Hear a Symphony” and “You Can’t Hurry Love,” all recorded in Motown’s cramped basement studio.

Only the Beatles had more No. 1 hits from 1964 to 1969. The Supremes went on worldwide tours and appeared on various TV programs, including “The Tonight Show” and then-popular variety shows such as “The Ed Sullivan Show,” “The Dean Martin Show” and “The Hollywood Palace.” They were credited with influencing countless musical acts, from Janet Jackson to Destiny’s Child and En Vogue.

The Supremes were not the first “girl group,” as they were commonly known at the time, to achieve success. Earlier groups, such as the Chiffons, the Crystals and Motown’s Martha and the Vandellas, had major hits — “but they would have loved to have our glamour,” Ms. Wilson quipped to the New York Times. In the early years, the three Supremes sewed their matching outfits themselves.

“We would go to Woolworth’s and buy our pearls,” Ms. Wilson said. “We’d buy Butterick patterns and make our own dresses.”

They soon became fashion trendsetters, with sleek matching gowns and elaborate hairstyles and wigs, and began buying their clothes at Saks Fifth Avenue.

“Those shimmery dresses — for the first time I think people saw women of color looking affluent on TV,” fashion writer Andre Leon Talley told the Times. “The Supremes were living the dream, looking impeccable and flawless to a fault.”

From 1964 to 1969, the Supremes produced 19 Top 20 hits, and had “limos, champagne, thousand-dollar dresses, and a complete entourage at our beck and call,” Ms. Wilson wrote in a 1986 memoir, “Dreamgirl: My Life as a Supreme.”

But internal fault lines were developing, she wrote, when it became clear Gordy was pushing Ross to the forefront at the expense of Ballard and Ms. Wilson. In 1967, Ballard was forced out and replaced by Cindy Birdsong. The same year, the group became officially known as Diana Ross and the Supremes.

Ms. Wilson did not even sing on the original recordings of the group’s final No. 1 hits, “Love Child” and “Someday We’ll Be Together,” both from 1969. Ross appeared for the last time with the Supremes in 1970.

For the next few years, the group kept performing, with Jean Terrell taking over the lead vocals, followed by a changing cast of singers. (Ballard died in poverty in 1976 without rejoining the Supremes.)

There were several hits without Ross, including “Stoned Love” and “River Deep, Mountain High,” but times and tastes were changing. Ms. Wilson, the last remaining original Supreme, stayed with the group until it disbanded in 1977.

Mary Wilson was born March 6, 1944, in Greenville, Miss. She moved to Detroit when she was about 3 to live with an aunt and uncle in Detroit. She believed they were her parents until her mother moved to Detroit a few years later.

As a girl, Ms. Wilson listened to her aunt and uncle’s record collection, absorbing everything from jazz to gospel to popular music. She said she was just as inspired by the movies of Doris Day as by the early rock-and-roll of Little Richard.

In elementary school, she sang in a talent show and soon began vocalizing with Ballard and later Ross and other girls in the neighborhood. They began to visit the Motown studio and occasionally sang backup on recordings for $2.50 apiece.

“We were Cinderellas,” Ms. Wilson told the Dallas Morning News. “It was a real little fairy tale.”

The fairy tale ended after Ross left the group and became a superstar. Ms. Wilson had long legal battles with Motown over management and money issues and found only modest success as a solo act.

After seeing “Dreamgirls,” a theatrical production about the behind-the-scenes drama of a group like the Supremes, Ms. Wilson wrote her first memoir, “Dreamgirl,” which was on the bestseller charts for months.

In it, she portrayed Ross as selfish and backstabbing and described the Svengali-like control Gordy exerted over his studio and particularly the women in the group.

“We were real human beings, not plastic dolls that Berry Gordy just wound up,” she told The Post.

There were several attempts to have a Supremes reunion tour with Ms. Wilson, Ross and Birdsong, but they fell apart over contractual problems. Ross toured in 2000 with two singers who were briefly in the group in the 1970s.

When the Supremes were inducted into the Rock & Roll Hall of Fame in 1988, Ms. Wilson was present for the induction ceremony, but Ross was not.

Ms. Wilson’s marriage to Pedro Ferrer, a onetime manager of the Supremes, ended in divorce. Their son, Rafael Ferrer, died in a car accident in 1994, in which Ms. Wilson was driving.

Survivors include two other children and a younger cousin Ms. Wilson later adopted; a sister; a brother; 10 grandchildren; and a great-granddaughter.

Ms. Wilson published another best-selling memoir in 1990 and a coffee-table book, “Supreme Glamour,” about the Supremes’ fashion styles, in 2019. That year, she also appeared on “Dancing With the Stars.”

Two days before her death, Ms. Wilson announced in a YouTube video that she was about to release new recordings in celebration of the Supremes’ 60th anniversary.

“For black America especially, we became everyone’s sister or daughter,” Ms. Wilson told author Edward Kiersh for his 1986 book “Where Are You Now, Bo Diddley?”

“Blacks didn’t have too many heroes in those days, but we gave people pride in themselves. We made their lives a little sweeter.”

An earlier version of this story incorrectly stated that Elvis Presley had more No. 1 hits than the Supremes between 1964 and 1968.