An Irishman, Finian, and his daughter Sharon, arrive in Rainbow Valley, a Southern town of tobacco sharecroppers in the state of Missitucky. The town has its own resident dreamer, Woody, who thinks that he might be able to put the town on the map by crossing mint with tobacco so that it'll grow mentholated. Finian's came to town because he's stolen a leprechaun's crock of gold and plans to plant it in the ground. But trouble arrives in the form of Og the leprechaun, who has followed Finian and wants his gold. Meanwhile, the bigoted Senator Billboard Rawkins, in an effort to stop progress in his state in the form of a new dam and hydroelectric system, plans to take the remaining parcel of land needed to stop the project. But the government's geologists reveal the Senator that gold has been detected on the property! Rawkins and his men confront the sharecroppers to seize their land using as an excuse an obscure law making it a felony for blacks and whites to live together.