The Rancho El Cajon land grant was issued in 1845, four years before California became a U.S. territory and the Mexican land grant system came under American legal scrutiny. María Antonia Estudillo de Pedrorena received the grant through the social and political mechanisms of late Mexican California, where family connections and political relationships determined who received land and how much. The Estudillo family was one of the most prominent in San Diego; the Pedrorenas were connected by marriage to that network. Miguel de Pedrorena, born in Madrid in 1808, had come to Alta California via Lima, Peru, in 1838 and established himself as a merchant, rancher, and eventual civic figure. He died in 1850, two years after California became American territory, leaving his wife holding the title to one of the region's largest land grants.

The land of Rancho El Cajon had previously been part of the agricultural territory of the California missions. Before the missions, it was Kumeyaay territory, part of a landscape that the indigenous people of the region had managed for thousands of years. "El Cajon" — the Spanish name, given by colonizers who saw the valley's boxlike geography — recorded a geographical observation rather than a history. The rancho's boundaries encompassed what are now the cities of El Cajon, Santee, Lakeside, and La Mesa, an area that today contains hundreds of thousands of people in suburban development built largely in the postwar decades.

After California statehood, Mexican-era land grants required confirmation by the U.S. Land Commission and, frequently, by the federal courts. The Rancho El Cajon grant was eventually confirmed and patented in 1876, following a Supreme Court decision. By then, most of the original grant had passed out of the Pedrorena family's hands. Isaac Lankershim, a developer whose name also appears prominently in the history of the San Fernando Valley in Los Angeles, purchased the bulk of the rancho in 1868. The fragmentation of large Mexican-era ranchos into smaller holdings, sold to Anglo-American settlers and developers, was the mechanism by which California's rural landscape became its suburban one.

El Cajon the city has grown far beyond anything that the Spanish colonizers who named the valley, the Mexican governor who granted it, or the Pedrorena family who held it could have imagined. The valley that looked like a drawer now contains a major regional airport (Gillespie Field), a substantial population of East African refugees, community colleges, shopping centers, and the full apparatus of American suburban life. The name survived all of it. El Cajon is still the drawer, still the valley folded into the hills — the Spanish observation about the landscape outlasting every political arrangement that has since governed it.