She died Wednesday of natural causes at her Sherman Oaks home, where she had lived since 1946, Roger C. Memos — writer-director of the documentary Marsha Hunt’s Sweet Adversity confirmed.

Hunt also appeared opposite Mickey Rooney in the best picture Oscar nominee The Human Comedy (1943) during a period in which she was known as “Hollywood’s Youngest Character Actress.”

Playing Walter Brennan’s sweetheart in Joe and Ethel Turp Call on the President (1939), Hunt aged from age 16 to 65 onscreen.

She portrayed the dowdy sister Mary Bennet in Pride and Prejudice(1940), and in Anthony Mann’s film noir Raw Deal (1948), she was the good girl opposite Claire Trevor.

In the 1971 Johnny Got His Gun, penned by blacklisted writer Dalton Trumbo, Hunt played the mother of Timothy Bottoms’ quadruple-amputee character.

Though she never achieved the stardom of some of her co-stars, Hunt was proud of her career, especially early on. “Before I was 30, I had played four aging roles, and I was Hollywood’s youngest character actress … no two roles alike,” she told the website Ms. in the Biz in 2015.

In 1947, Hunt and her second husband, screenwriter Robert Presnell Jr., joined the Committee for the First Amendment, which challenged the legality of the House Un-American Activities Committee that was seeking to flush communists out of the entertainment industry.

The committee, which also included Humphrey Bogart, Lauren Bacall, Danny Kaye, John Huston and other Hollywood liberals, chartered a plane to Washington to sit in on the HUAC hearings and support 19 creatives who had been under scrutiny.

“You know, I was never interested in communism,” she said 2004 interview. “I was very much interested in my industry, my country and my government. But I was shocked at the behavior of my government and its mistreatment of my industry. And so I spoke out and protested like everyone else on that flight. But then I was told, once I was blacklisted, you see, I was an articulate liberal, and that was bad. I was told that in fact it wasn’t really about communism — that was the thing that frightened everybody — it was about control and about power.

“The way you get control is to get everyone to agree with whatever is proper at the time, whatever is accepted. Don’t question anything, don’t speak out, don’t have your own ideas, don’t be articulate about it, don’t ever be eloquent, and if you ever be one of those things, you’re controversial. And that’s just as bad, maybe worse, than being a communist. Which was still quite legal to be, you know: the Communist Party was still legal in America, running candidates for public office. But you lost your career, your good name, your savings, probably your marriage, your friends, if you had been a communist. It was appalling, just appalling.”

She was born Marcia Virginia Hunt in Chicago on Oct. 17, 1917. Her father, Earl, was an insurance executive and her mother, Minabel, a vocal coach. She and her family moved to New York City, and she graduated from the Horace Mann School for Girls at age 16.

She was signed by the Powers Agency, becoming a sought-after “Powers Girl” and learning how to pose and behave in front of a lens.

Friends with photographers-turned-publicists Robert and Sarah Mack, Hunt moved to Hollywood at 17, signed with Paramount when her agent, Zeppo Marx, got her $250 a week and landed the female lead in her first movie, The Virginia Judge (1935). She appeared as an ingenue and love interest in several films — John Wayne romanced her in Born to the West (1937) — but the studio declined to renew her contract in 1938.

She landed at MGM in The Hardys Ride High (1939) and went on to appear for the studio in The Trial of Mary Dugan (1941) as a Brooklyn chorus girl; in Kid Glove Killer (1942), director Fred Zinnemann’s first U.S. feature; in the World War II drama Cry ‘Havoc’ (1943); and as the top-billed title character in the Jules Dassin romantic comedy A Letter for Evie (1946).

Exhibitors poll had placed her among the “Top 10 Stars of Tomorrow” — others on the list included Roddy McDowall, Gloria DeHaven, Sidney Greenstreet, June Allyson and Barry Fitzgerald — and when she wasn’t acting, she was serving as a hostess at the famed Hollywood Canteen for American servicemen.

In 1948, Hunt made her stage debut in the Hollywood-set Joy to the World, directed by Jules Dassin; two years later, she was back on Broadway in George Bernard Shaw’s The Devil’s Disciple and graced the cover of Life magazine.

After Devil’s Disciple closed, Hunt departed for Europe, but when she returned, Red Channels had been published, and her career — she had made more than 50 films by then — would never be the same.

She guest-starred on such shows as The Ford Television Theatre, Climax! and Alfred Hitchcock Presents, was a regular on the short-lived 1959 series Peck’s Bad Girl and later appeared on Gunsmoke, The Twilight Zone, Ben Casey, My Three Sons, Ironside, Murder, She Wrote and Star Trek: The Next Generation.

Hunt was a member of the SAG board and worked on various progressive committees; one counseled actress Olivia de Havilland in her groundbreaking legal case against the studio system and Warner Bros., and another petitioned to hire minority actors outside of stereotyped roles.

In 1955, a trip around the world opened her eyes to the plight of Third World nations, and she threw herself into humanitarian efforts, making appearances on behalf of the United Nations and becoming what she called a “planet patriot.”

In April 2015, she was named the inaugural recipient of the Marsha Hunt for Humanity Award, created by Kat Kramer, the daughter of the director-producer Stanley Kramer.

Hunt was “one of the first major actresses in Hollywood to dedicate her life to causes,” Kat Kramer noted, “and she paved the way for Angelina Jolie, Sean Penn, Jane Fonda, Lily Tomlin, Patricia Arquette, Sharon Stone, George Clooney, Matt Damon, Don Cheadle, Tippi Hedren, Ed Begley Jr., Ed Asner and Martin Sheen — celebrities who use their fame as a voice for change.”

Hunt can be seen in all her glamour in the 1993 book The Way We Wore: Styles of the 1930s and ’40s and Our World Since Then, which features photos of her in many of her own clothes from the era.

Hunt moved to Sherman Oaks in 1946 and served as its honorary mayor for more than two decades. She and Presnell were married for 40 years until his death in 1986 at age 71. They had no children.

She is survived by a nephew, actor-director Allan Hunt, and other nieces and nephews. Donations in her memory may be made to L.A. Family Housing.

In 2008, Hunt starred in the 22-minute film The Grand Inquisitor, written and directed by Eddie Muller.

“To work with her was the most rewarding collaboration of my life. I suspect it always will be,” the host of TCM’s Noir Alley said after Raw Deal and The Grand Inquisitor played back-to-back on the cable channel last month. “She is simply the most exceptional human being I’ve ever known.”