One of the most outstanding examples of Spanish colonial architecture in the United States is the Mission of San Xavier del Bac outside of Tucson, Arizona. The mission was built between 1783 and 1797 and was originally established in 1692 by Father Eusebio Francisco Kino. See Wikipedia: Mission San Xavier del Bac. Restoration of the structure was completed in the late 1900s. It is a lovely place visit and the Mission is still used weekly for church services.