Kevin Costner is leaving Yellowstone to focus on his long-gestating passion project titled Horizon: An American Saga, a Western saga about the expansion of the American West. Despite Yellowstone's success, Costner has shown no interest in further involvement. He commissioned the story for Horizon in 1988 and has been working on it for over three decades. Costner is both starring in and directing the project and has invested a significant amount of his own money into it. The financial and critical outcomes of Horizon are of little importance to Costner compared to his dedication to the project.