Originally planned as a two-part television show titled The Family Band, the project was based on a book by Laura Bower Van Nuys. The memoir by Van Nuys, the youngest of the Bower children, described her family's brass band, their journey out of Missouri, and their frontier life in the Black Hills.
Walt Disney had asked the Sherman Brothers for their help on the project, feeling the story was too flat. The Shermans wrote the song "The One and Only, Genuine, Original Family Band", which was ultimately used as the title of the motion picture. After hearing the song, Disney decided to add more songs to the film and turn it into a musical. In all, the Sherman Brothers wrote eleven songs for the film, though Robert reportedly did so under protest, believing the subject matter too mundane to be made into a feature-length musical film.
The Bower Family Band petitions the Democratic National Committee to sing a rally song for President Grover Cleveland at the party's 1888 convention. On the urging of Joe Carder, a journalist and suitor to eldest Bower daughter Alice, the family decides instead to move to the Dakota Territory. There, Grandpa Bower, a staunch Democrat, causes trouble with his pro-Cleveland sentiments. The Dakota residents are overwhelmingly Republican, and hope to get the territory admitted as two states (North and South Dakota) rather than one (so as to send four Republican senators to Washington rather than two). Grandpa's actions result in family strife, including nearly costing Alice her position as the town's new school teacher. The budding romance between Joe and Alice also suffers. In the end more ballots are cast for Cleveland, but Republican nominee Benjamin Harrison nonetheless wins the presidency—the first time in the nation's history that the Electoral College reverses the popular vote. Before he leaves office Cleveland grants statehood to the two Dakotas, along with two Democrat-voting territories, evening the gains for both parties. The Dakotans, particularly the feuding young couple, resolve to live together in peace.
- Walter Brennan - Renssaeler Bower
- Buddy Ebsen - Calvin Bower
- John Davidson - Joe Carder
- Lesley Ann Warren - Alice Bower
- Janet Blair - Katie Bower
- Kurt Russell - Sidney Bower
- Steve Harmon - Ernie Stubbins
- Richard Deacon - Charlie Wrenn
- Wally Cox - Wampler
- Debbie Smith - Lulu Bower
- Bobby Riha - Mayo Bower
- Smith Wordes - Nettie Bower
- Heidi Rook - Rose Bower
- Jon Walmsley - Quinn Bower
- Pamelyn Ferdin - Laura Bower
- John Craig - Frank
- William Woodson - Henry White
- Goldie Hawn (as Goldie Jeanne Hawn) - Giggly Girl
- Jonathan Kidd - Telegrapher
- Hank Jones - Town Delivery Boy (uncredited)
- Butch Patrick - Johnny (uncredited)
- "The One and Only, Genuine, Original Family Band" The film opens with Grandpa conducting all ten members of the Bower family, each playing a different musical instrument. Practicing in their barn, the family dances among the animals and hay, boasting of their unique talents and versatility.
- "The Happiest Girl Alive" Alice expresses her intense emotions over receiving her latest letter from suitor Joe Carder.
- "Let's Put It Over with Grover" The Bowers perform this Grover Cleveland campaign song to a representative from the Democratic National Committee.
- "Ten Feet off the Ground" Ecstatic at the prospect of performing at the National Convention, the family band engages in an impromptu celebration. They sing about the feeling which only music can bestow, figuratively lifting them "Ten Feet off the Ground". (This was one of two songs from the film covered by Louis Armstrong later in 1968.)
- "Dakota" Joe Carder entices local Missouri families, singing about the marvels of the Dakota Territory. ("Dakota" is similar in style to the title song of the Oklahoma! and was once considered as a candidate for "state song" for South Dakota.)
- "'Bout Time" Joe Carder expresses his devotion to Alice, telling her it's "'Bout Time" they were engaged, she responds in kind, and the two sing this duet. (This song was covered by Louis Armstrong and was later featured in the 2005 film, Bewitched.)
- "Drummin' Drummin' Drummin'" Grandpa Bower recounts the tale of a young drummer boy during the Civil War, inspiring all the children in the school house that they too can stand their ground and make a difference.
- "West o' the Wide Missouri" On election night, locals dance and celebrate their part in American expansionism West o' the Wide Missouri.
- "Oh, Benjamin Harrison" The Republicans in town have their own campaign song; they sing their praise for Benjamin Harrison, who is "far beyond comparison."