WASHINGTON — Former Rep. Lindy Boggs of Louisiana, who used the soft-spoken grace of a plantation lady to fight for civil rights during nearly 18 years in Congress, has died. She was 97.

Her daughter, ABC News journalist Cokie Roberts, says her mother died Saturday of natural causes at her home in Chevy Chase, Md.

Boggs’ years in Congress started with a special election in 1973 to finish the term of her husband, Hale, whose plane disappeared over Alaska six months earlier. Between them, they served a half-century in the House.

When she announced her retirement in 1990, she was the only white representing a black-majority district in Congress.

Boggs later served three years as ambassador to the Vatican in the Clinton administration.