Director Robert Rossen filmed in an unusual manner. Nobody in the cast had a script. Rossen let them read it once and took it away from them. According to Broderick Crawford, "We really had to stay on our toes."

Mercedes McCambridge was cast after she got angry with the producers. She and other actresses were kept waiting in an office in New York City during open auditions. McCambridge told the producers off and stormed out of the office. They called her back and eventually cast her because she fit the part of Sadie.

According to Broderick Crawford, "During the filming, we never mentioned the name of Huey Long on the set. That was the unspoken law at the studio."

Residents of the area around Stockton, California, were used as extras in the film; often, director Robert Rossen would give them speaking parts and film the "rehearsals" to get a more spontaneous effect.

To prepare for the role of Willie Stark, Broderick Crawford watched newsreels of Huey Long, the former Louisiana senator and governor on whose life the novel was loosely based.

Producer-director Robert Rossen offered the role of Willie Stark to John Wayne. Rossen sent a copy of the script to Wayne's agent, Charles K. Feldman, who forwarded it to Wayne. After reading the script, Wayne sent it back with an angry letter attached. In it, he told Feldman that before he sent the script to any of his other clients, he should ask them if they wanted to star in a film that "smears the machinery of government for no purpose of humor or enlightenment," that "degrades all relationships," and that is populated by "drunken mothers; conniving fathers; double-crossing sweethearts; bad, bad, rich people; and bad, bad poor people if they want to get ahead." He accused Rossen of wanting to make a movie that threw acid on "the American way of life." If Feldman had such clients, Wayne wrote that the agent should "rush this script... to them." Wayne, however, said to the agent that "You can take this script and shove it up Robert Rossen's derrière . . . " Wayne later remarked that "To make Huey Long a wonderful, rough pirate was great . . . but, according to this picture, everybody was shit--except for this weakling intern doctor who was trying to find a place in the world." Broderick Crawford, who had played a supporting role in Wayne's Seven Sinners (1940), eventually received the part of Stark. In a bit of irony, Crawford was Oscar-nominated for the part of Stark and found himself competing against Wayne, who was nominated the same year for Sands of Iwo Jima (1949). Crawford won the Best Actor Oscar, giving Rossen the last laugh.

Al Clark did the original cut but had trouble putting all the footage that Robert Rossen had shot into a coherent narrative. Robert Parrish was brought onboard by Rossen and Harry Cohn, to see what he could do. Since Rossen had a hard time cutting anything he shot, after several weeks of tinkering and cutting, the movie was still over 250 minutes long. Cohn was prepared to release it in this version after one more preview, but this threw Rossen into a panic, so Rossen came up with a novel solution. Rossen told Parrish to "[s]elect what you consider to be the centre of each scene, put the film in the synch machine and wind down a hundred feet before and a hundred feet after, and chop it off, regardless of what's going on. Cut through dialogue, music, anything. Then, when you're finished, we'll run the picture and see what we've got". When Parrish was done with what Rossen had suggested, they were left with a 109-minute movie that was more compelling to watch. After the film won its Academy Award for Best Picture, Cohn repeatedly gave Parrish credit for saving the film, even though Parrish only did what Rossen told him to do.

Film debut of Mercedes McCambridge.

Robert Penn Warren's novel, upon which the film was based, was published in 1946. It went on to win the Pulitzer Prize. Writer-director Robert Rossen purchased the film rights himself, and was then able to broker a deal with Columbia Pictures. He shifted the focus of the novel from the Jack Burden character (played by John Ireland) to Willie Stark.

After Robert Rossen took the Fifth Amendment when he was questioned by the House Committee on Un-American Activities in 1951, Columbia broke all connections with him and bought all rights and residuals in the films he made for the studio, including this one. In 1953, Rossen again appeared before the committee and named fifty-seven people in Hollywood who had at one time belonged to the Communist Party.

According to Don Siegel in his memoirs, Broderick Crawford was drunk on most scenes of the film. But he was ready and brilliant for each of the performances he finally pulled.

John Derek completed this film prior to Knock on Any Door (1949), but that was released first and is generally considered to be Derek's debut film.

The first film to win both the Best Actor and Best Supporting Actress Oscars.

The campaign montages were shot by Don Siegel.

Portions of the film were shot on location in small towns near Stockton in central California.

Included among the American Film Institute's 1998 list of the 400 movies nominated for the Top 100 Greatest American Movies.

Mercedes McCambridge's Best Supporting Actress Oscar win is one of the rare occasions where an actor or actress has won an Academy Award on their debut.

In adapting the novel for the screen, Robert Rossen made many changes: While the focus of the film is the character of Willie Stark, Jack Burden is the focus in the novel. Willie's political party is unidentified in the picture, as is the state that elects him to political office.

Harry Cohn wanted Spencer Tracy for the role of Willie Stark. Robert Rossen disagreed, saying that the audience might like Tracy too much.

Was the last film for more than 50 years to win the Academy Award for Best Picture that did not also win an Oscar for either writing or directing, until Gladiator (2000). It would occur again just two years after "Gladiator" with Chicago (2002).

In 1948, Norman Corwin was hired to write a draft of the screenplay. After the release of the film, questions arose about the extent of Corwin's contributions to the completed film, but the Screen Writers Guild judged Rossen to be the sole writer.

Humphrey Bogart was considered for the lead role.

In the original manuscript, Willie's last name is Talos, not Stark. When the novel was first published, the name was Stark. In 2001, the novel was reprinted with Stark's name changed back to Talos, among other changes.

Mercedes McCambridge's Best Supporting Actress Oscar winning performance was the only nominee in the category in a Best Picture nominee that year.

Won the Directors Guild of America (DGA) Award for Outstanding Directorial Achievement in Motion Pictures in 1950. The previous year's ceremony in 1949 was the the very first in the Guild's history. For the 1949 awards, the DGA had used a non-calendar year honoring films released in both 1948 and early 1949, unlike the Academy Awards. Both the 1949 and 1950 DGA winners, A Letter to Three Wives (1949) and All the King's Men (1949) respectively, competed for the 1950 Academy Award for Best Director, which was awarded to Joseph L. Mankiewicz for "A Letter to Three Wives", the 1949 DGA winner. This explains why the heavily favored Robert Rossen did not win for directing "All the King's Men" at the Oscars, however the film was awarded Best Picture.

Features the only Oscar nominated performances of Broderick Crawford (for which he won Best Actor) and John Ireland.

The only film to be nominated for Best Supporting Actor and Supporting Actress Oscars that year.

Anne Seymour's debut.