Interior shots were filmed at Paramount Studios in Los Angeles, while exteriors were largely filmed at the nearby Big Sky Ranch in Simi Valley, where the town of Walnut Grove had been constructed. Many other filming locations were also used during the course of the series, including Old Tucson Studios and various locations in Sonora, California. Many of the exterior shots of Walnut Grove and the other Minnesota towns shown in the series include noticeable mountainous terrain in the background scenery. In reality, however, the southern Minnesota landscape where the show is supposed to take place includes no tall mountains.