The mission’s site was an elevated plateau in a bend near the base of Mission Peak, with a broad plain beneath it sloping gently across the nine-mile stretch to the southern shores of the San Francisco Bay.

With a practiced eye [Father Lasuen] could see that the acres immediately below the plateau would best serve as fields for grain and corn.  The lower and more southerly reaches of the terrain toward Los Cerritos, the site of the present Dumbarton Bridge, northward to the present location of Oakland, and easterly to the general neighborhood of Mount Diablo offered teeming acres of rich pasturage for the cattle.  The lofty mountain valleys and meadows in the rear of the mission, watered by the Calaveras Creek and abundant springs, would sustain tens of thousands of sheep.  The plateau itself afforded ample space not only for the building of the mission, but also for its orchards, vegetable gardens, and promenades.  Behind the orchard site, on a sunny stretch of rolling hills rising from the four hundred to the five hundred foot level, the mission grapes would purple without injury from the frosts of winter. At nearby Agua Caliente (now Warm Springs), there bubbled from the earth copious springs of hot medicinal waters.

Father President directed some of the escort to construct a large cross on the ground, and others to build in the open an enramada, of “bower of branches,” with an altar in its shelter, in preparation for the ceremony of founding the mission set for the next day.

“Very early in the morning,” the first day of the week, June 11, 1797, the Feast of the Most Holy Trinity, the reverend Fathers, the Spanish soldiers, and the Loreto Indians assembled for the dedicatory ceremony.  The unusual stir in the camp, the ringing of the bell, the firing of the muskets, the smoke of the incense, the lighting of the Mass candles, the sight of the beautiful vestments of the priests – all attracted groups of [Indians] to the scene.