The San Diego Viejo Plaza site is California Historical Landmark No.

The plaza (town square) was the center of the Pueblo de San Diego, founded in 1835 in Alta California.

[2][3][4] The major buildings and houses of the Pueblo of San Diego were built around the town square.

Pueblo status was granted after a petition was sent to Governor José Figueroa and endorsed by Commandant Santiago Arguello.

[8] The United States acquired Alta California and San Diego through the Mexican–American War and the Treaty of Guadalupe Hidalgo.

The Works Progress Administration did restoration in the 1930s of a few remaining buildings, including the Casa de Estudillo.

[2][15] Early mayors, called alcalde, of the Pueblo de San Diego, included: Juan María Osuna, Santiago Argüello, José Antonio Estudillo, Rosario E. Aguilar, Jesús Moreno, and José María Alvarado.