Joan Marie Johnson, a founding member of the musical trio the Dixie Cups, whose hit “Chapel of Love” unseated the Beatles from the top of the Billboard 100 in 1964, died on Sunday at her home in New Orleans. She was 72.

The cause was heart disease, other members of the group said.

The Dixie Cups began when Ms. Johnson invited Barbara Ann Hawkins to sing with her in a high school talent show in New Orleans. “I was on my way to the grocery store and she stopped me and said, ‘I heard you sing,’” Ms. Hawkins said.

Barbara Ann’s sister, Rosa Lee Hawkins, soon joined them. Ms. Johnson later discovered that the Hawkins sisters were her cousins. All had grown up in the city in the Calliope housing project.