On September 7-8, 1769, Gaspar de Portola traveled through the San Luis Obispo area on his way to rediscover the Bay of Monterey. The expedition's diarist, Padre Juan Crespi, recorded the name given to this area by the soldiers as Ilano de los Osos, or the Level of the Bears (Bear Plain) as this was an area with an abundance of bears. Since then, various translations of Crespi's diary have called this area La Canada de los Osos (The Canyon of the Bears) which has been further mistranslated as the Valley of the Bears.
Father Junipero Serra decided that this area would be an ideal place for a fifth mission. There were abundant supplies of food and water, the climate was very mild and the local Chumash were very friendly. With soldiers, muleteers and pack animals carrying supplies, Father Serra set out on a journey to the area. On September 1, 1772 he celebrated the first Mass with a cross erected near San Luis Creek. The next day he departed for San Diego, leaving Fr. Jose Cavaller with the difficult task of building the mission. Fr. Cavaller, five soldiers and two neophytes began building what is today called Mission San Luis Obispo de Tolosa.