Just before Christmas, the editor of the Morgan's Creek newspaper anxiously calls Governor McGinty (Brian Donlevy) to announce some astonishing news. Although McGinty is impatient, the editor begins to relate a long-winded story:

After reading an editorial in the Morgan's Creek newspaper on sudden war marriages, grumpy town policeman Officer Kockenlocker (William Demarest) forbids his nearly adult daughter Trudy (Betty Hutton) from attending a farewell dance for soldiers. Trudy, convinced that dating soldiers fulfills her patriotic duty, rebels and pretends that her childhood friend, homely, stuttering Norval Jones (Eddie Bracken), whose enlistment has been rejected because of his high blood pressure, is taking her out to the movies. While Trudy attends the dance, Norval reluctantly sits through three features at the movie theater. Trudy, meanwhile, drinks champagne and dances with soldier after soldier.

While dancing the jitterbug at one point, Trudy is knocked on the head by a chandelier. When she finally picks Norval up at eight in the morning, she does not remember where she has been, and Norval takes the brunt of her father's anger. Later, while talking with her fourteen-year-old sister Emmy (Diana Lynn), Trudy vaguely recalls using an assumed name and marrying someone the night before. Her suspicions are confirmed by the wedding band she now wears. Some time later, Trudy's worst fears are realized when she learns that she is pregnant. Still completely unaware of the identity of her husband, Trudy consults with lawyer E. L. Johnson (Alan Bridge), who says that her marriage is legal, even though she used an assumed name and has no idea who the groom was.

Although she previously spurned Norval's awkward romantic advances, Trudy now encourages him, and Norval, who has been devoted to Trudy since childhood, is stunned by her sudden change of heart. However, Trudy's conscience will not allow her to deceive earnest Norval, and she confesses her predicament to him. Trudy then sincerely falls in love with Norval, but refuses to marry him as it would constitute bigamy. Kockenlocker, however, is unaware of his daughter's situation and intimidates Norval into the marriage, as the town is already gossiping about Trudy. Hoping she can obtain a new marriage license with the name of her first husband on it in order to get a divorce and then marry Norval, Trudy sneaks away with Norval.

At the Honeymoon Hotel, twenty-five miles from Morgan's Creek, Trudy registers under her real name, and Norval, wearing a World War I cavalry uniform, uses the name Ratzkiwatzki, which Trudy believes is her first husband's name. After the hasty ceremony is performed by the proprietor, however, Norval signs his real name to the license, and the proprietor accuses him of having abducted Trudy, who is a minor, and impersonating an officer. Norval and Trudy are brought home by a bevy of police, who have brought nineteen charges against Norval, and refuse to listen to Trudy's explanation.

Kockenlocker is forced to imprison Norval, and as a gesture of kindness, the proprietor tears up the marriage certificate. Kockenlocker realizes that this was a mistake, however, when Trudy admits that she is pregnant. Kockenlocker then encourages Norval to escape, but he is too honest and refuses until Kockenlocker forcibly removes him from jail. Norval then slips into the bank where he works and takes $900 from his account, intending to search for Ratzkiwatzki. Norval escapes in Kockenlocker's car after he sets off the alarm, and Emmy and Trudy tie up their father and knock him out to mitigate his involvement in the break-in.

Having brought McGinty up to date, the editor finally reveals that Norval, who is still considered an escaped prisoner and bank robber, has returned from his unsuccessful trek searching for Trudy's husband, and was picked up by police after discovering that Kockenlocker was fired and moved out of town six months earlier. Trudy learns of Norval's return and insists on returning to Morgan's Creek to publicly state the truth, but her speech is preempted when she goes into labor and gives birth to sextuplets, thereby making national headlines. McGinty drops all charges against Norval, arranges for Trudy's first marriage to be annulled, and insists that she has been married to Norval all along. The effects of the birth of sextuplets are felt around the world, and Norval himself becomes hysterical when he learns how many children will bear his name.

In 2001, "The Miracle of Miracle's Creek" was selected for preservation in the United States National Film Registry by the Library of Congress as being "culturally, historically, or aesthetically significant".

Premiere Magazine voted this movie as one of "The 50 Greatest Comedies Of All Time" in 2006.

The film ranks #54 on the AFI's 100 Years... 100 Laughs list of the top 100 funniest films in movie history.

When the film was released, it was such a huge hit, it was literally standing room only for many performances.

Eddie Bracken revealed in a 2000 interview that he was relunctant to do this film: "I didn't want to work with Betty Hutton anymore, merely because [Paramount Pictures head] Buddy De Sylva was using me to build up Betty. She got her first picture with me, and they knew that I would help her with the camera angles, keeping your face in front, and a lot of other things, and I would give her all the tricks. And she and I got along beautifully together, except when I went to see The Fleet's In, there were three or four extra songs put in [for Hutton] that none of us knew about. Dorothy Lamour was mad. Bill Holden was mad. I was mad, too. Then we did Happy Go Lucky, and the same thing happened. And then Star Spangled Rhythm. They're building her up to be the big star. And there's nothing wrong with that because she deserved every second of it. Betty's a great gal. We have been friends from day one. But I rebelled. And when The Miracle of Morgan's Creek came along, I turned it down. And they told Buddy why. And Preston Sturges called me and he says, 'What's this I hear that you don't want to do a Preston Sturges movie?' And I said, 'I would love to do a Preston Sturges movie.' And he said, 'Well, you didn't like this script?' And I said, 'I didn't read it, Mr. Sturges. The reason I'm not doing it is because --' and I told him about Betty's songs that were put in by Buddy De Sylva. He didn't like Buddy De Sylva anyway, and he said, 'Look: There are no Betty Hutton songs in this except one that I wrote where she has to sing as a bass and we're using a man with a bass voice. That's the only song she'll be mouthing and I will not write another because it's not a musical we're doing here, it's a serious comedy.' I said, 'You'd promise me that?' He said, 'Do you want it in writing?' I said, 'No, instead of that, let me read the script so that I will know my lines when I get there because I will do it. And thank you very much for wanting me and thank you for calling.' When I read the script, it was written to make Betty Hutton a star. [Her part] was at least eight times the size of my part. So I looked at this and I study it and I study it because now I'm gonna do exactly what I want to do, not to steal the picture but to steal the scenes that I'm in, or do everything I could do to steal them. And that's what I did. I'm not the kind of actor that goes out and counts the lines; it was just that one picture and merely because I was fighting Buddy De Sylva -- whom I loved, incidentally. But I didn't agree with him using people; he used Bing Crosby and Bob Hope and everybody else to make Betty Hutton a star, and to me Betty Hutton was a star no matter what. But when we're used to build her up without them even thinking about us, you get pretty upset about it. You don't want to lose your own career. "

Eddie Bracken also discussed the scene where he and Betty attempt to marry: "Porter Hall is trying to marry us and she starts to stutter, just like I do. And I'm thinking, What's she doing here? She was ad libing. But at the same time, I was going right along with her because it was right on target. Sturges didn't know she was gonna do it, I didn't know she was gonna do it, but it was right on. It took us at least 10 takes [to finish the scene] what with people breaking up. On the ninth take or the eighth take or whatever the hell it was, Sturges got up and bawled out every single person on the set. 'What the hell do you think you're doing here? This is a movie, we're making it and we want it to be honest. Cut out the laughter!' So now we're all scared stiff because he's so mad. It was called for, too, because we were having so much fun giggling, we'd never get the scene done. Then, finally, we go into it and Betty and I are going strong, doing it great because we're playing it dead serious, and Sturges falls off the camera laughing. He breaks up. And he says, 'Well, we'll all have some coffee and forget this and we'll come back and pick it up later'. There was so much fun with that man. Dead serious, no question about it. Mean sometimes. He was Lucifer and he was Jesus Christ in one man."

The character Gov. McGinty is Dan McGinty, from the earlier film by Preston Sturges, "The Great McGinty" (1940).

"The Miracle Of Morgan's Creek" was loosely remade in 1958 with Jerry Lewis as "Rock-A-Bye Baby".