Philadelphia in the summer of 1876 and lots of celebration to mark America's first hundred years. The Rogers family are visited by their aunt Zenia (Constance Bennett), who brings with her a young Frenchman, Philippe Lascalles (Cornel Wilde), who is in charge of the French pavillon. Rogers family daughters, Julia (Jeanne Crain) and Edith (Linda Darnell), fall in love with Philippe, while their father, Jesse Rogers (Walter Brennan), tries to promote his inventions and hang onto his railroad job. With Zenia's help, he does both, while Julia wins the love of Philippe and Edith finally says yes to her devoted suitor Dr. Ben Phelps (William Eythe).