In 1769, Spanish Franciscan missionary Father Junípero Serra arrived in present-day San Diego, California, tasked with establishing a series of missions to aid the Spanish colonial effort. Mission San Diego de Alcalá, named after the Spanish city of Alcalá, was the first of these missions, marking the beginning of California's mission system. The mission was strategically located near a water source and fertile land, making it conducive for agriculture and settlement. Serra and his companions, part of the Portola expedition, aimed to integrate the local Kumeyaay people into the Spanish mission system, promoting both Christianity and Spanish cultural practices. The mission included a church, living quarters for the missionaries, and space for the local Indigenous population. In the following years, it served as a base for further missions and helped establish permanent European settlements in the area.

The mission's development was marked by both cooperation and conflict with the local Indigenous tribes. While some Kumeyaay engaged with the missionaries, many resisted, leading to complex relationships characterized by periods of collaboration and strife. Gradually, the mission grew into a community hub, with agriculture and new trades being introduced by the Spanish settlers. This transformation set the stage for the eventual establishment of the city of San Diego, which would become California's first major urban area. The mission's cultural impact and architectural footprint can still be seen in modern San Diego, where the mission's church now serves as a central historical site.