Previous to the founding of Mission Santa Inés, eighteen Missions had been established. Father Junipero Serra, followed by other Missions along the California coast, founded the first, Mission San Diego de Alcala, in 1769. After Father Serra's death in 1784, Fr. Fermin de Lasuen continued the project.
The founding of a Mission between La Purisima and Santa Barbara had been considered by the Missionary Franciscan fathers for several years. An inland Mission, north of Santa Barbara, would solidify their work in the area. They would be able to take advantage of the Chumash Indians' already favorable disposition to being converted to Christianity. In addition, the militant Indian tribe, the Tulares, lived to the northeast, just beyond the region controlled by the Chumash. A Mission in the Santa Ynez Valley would secure the region and create a buffer zone.
After completing the initial coastal chain of Missions to the north, Father Lasuen directed Father Estevan Tápis of Mission Santa Barbara to accompany Captain Felipe de Goycoechea to survey possible Mission sites northeast of the coastal mountains. In the fall of 1798, the expedition surveyed the Calahuasa rancheria (presently the Santa Ynez Indian Reservation) and another Chumash site called Alajlapu (presently Solvang). Father Tápis reported that there were 325 dwellings at 14 sites at Calahuasa and Father Lasuen reported the findings to Governor Diego Borica. In turn, the Spanish viceroy, Iturrigaray approved Calahuasa as a suitable site for a new Mission.
It would be 6 years before the Franciscans could establish their new Mission. The governor died, so approval was then needed from his successor, Jose de Arrillaga, in Baja California. Unfamiliar with the area, Governor Arrillaga wrote to Father Lasuen in April 1803 concerning the number of guards that would be needed for the new Mission. By the time the letter made its way to Santa Barbara, Father Lasuen had died. Father Estevan Tápis was now Presidente of the Missions. He responded to Arrillaga's letter, detailing the number of Indians in the area and the activities of a small group of Indian outlaws who had been committing murders throughout the region. In September, the Father Guardian of the Franciscan order came from Mexico to survey the site and determined that a guard of 6 men would be sufficient to protect the Mission.