Gladys Horton, who co-founded the 1960s Motown group The Marvelettes and sang on hits including "Please Mr. Postman," has died in Los Angeles at age 66.

Her son, Vaughn Thornton, says Horton died Wednesday night in a Sherman Oaks nursing home where she had been recovering from a stroke.

Video: The Marvelettes sing "Please Mr. Postman"

Horton was a teenager in the Detroit suburb of Inkster when she and some friends formed a group they called "The Casinyets," which was short for "can't sing yet."

When Georgia Dobbins had to leave, Horton became lead singer. The group changed its name to The Marvelettes, and Horton was 15 when Motown released "Please Mr. Postman" in 1961. "Postman" reached No. 1 on the Billboard Hot 100 on Dec. 16, 1961 and was the first No. 1 for Berry Gordy's Motown Record Corporation.

The Marvelettes went on to chart a total of 23 Hot 100 hits, including "Postman," "Playboy" (No. 7), "Beechwood 4-5789" (No. 17) and "Don't Mess With Bill" (No. 7). Horton was replaced as lead singer in 1965 and left the group two years later.

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(Additional reporting by Monica Herrera,