The adventures of Ben Cartwright and his sons as they run and defend their Ponderosa Ranch while helping the surrounding community. Bonanza is an NBC television western series that ran from 1959 to 1973. Lasting 14 seasons and 431 episodes, Bonanza is NBC’s longest-running western, and ranks overall as the second-longest-running western series on U.S. network television (behind CBS’s Gunsmoke), and within the top 10 longest-running, live-action American series.