Hazel Dickens, a folk singer and bluegrass musician who advocated for coal miners, has died. She was 75.

Dickens died Friday morning at a hospice in Washington, D.C., of complications from pneumonia. Her death was confirmed by Ken Irwin, a founder of Rounder Records, her label for about 40 years.

Dickens became a fixture in the bluegrass circuit in the 1960s and ’70s with her musical partner, Alice Gerrard. The duo performed as Hazel & Alice. They were among the first prominent female bluegrass performers.

Dickens’ music was later featured in the Oscar-winning 1976 documentary, “Harlan County U.S.A.,” about Kentucky coal miners, and John Sayles’ 1987 drama, “Matewan.” Irwin said Dickens will be remembered for giving voice to coal miners.