Founded in 1818 as a Spanish colonial sub-mission of Mission San Diego de Alcalá, Santa Ysabel Asistencia stood in the mountains east of San Diego near Elcuanan as both a religious outpost and a stopping place on inland travel routes. By 1821 it included a chapel, granary, adobe houses, and cemetery, serving about 450 Luiseño and Diegueño neophytes. After secularization in 1834, its isolation hastened decline, though travelers, soldiers, and mail lines continued to pass through. The original buildings disappeared, but the site remained important through its rancho-era connections, the story of its historic bells, and the later Mission Revival chapel built after land was returned to the Roman Catholic Church.