But it is not entirely unique. South of the border in Sonora, it has a twin: La Purisima Concepción de Nuestra Señora de Caborca. The two churches have the same three-part façade, the same two bell towers (though Caborca's right-side tower has the dome that's mysteriously missing at San Xavier). And both were constructed with "rubble-filled walls," as Gloria Fraser Giffords writes in her magisterial book, Sanctuaries of Earth, Stone and Light: The Churches of Northern New Spain, 1530-1821.
Built about 10 years apart in the late-18th century, with San Xavier coming first, the two missions are so similar that they may have had the same architect, Giffords notes. Even so, there are differences. Where San Xavier is elegant and slender, its three front sections equal in size, Caborca is a tad squat, with the two overly blocky side sections squeezing in the narrow central entrance. It's as though a divine architect had gently pressed down the roof with a giant hand.
The two churches are among hundreds that Giffords examines in this immense scholarly book, which she has been researching for 20 years. She covers three centuries of Spanish colonial church-building, zeroing in on the most active 150 years, from the late 1600s to the early 1800s. She's given herself the monumental task of surveying the architecture, paintings and church furnishings of missions all over Northern New Spain, a vast region that went as far north as present-day Wyoming and as far south as San Luis Potosí in Mexico.
A Tucson author who's a well-known art conservator and authority on Spanish colonial art, Giffords argues that local and regional differences helped create variable local styles, even when--as in the case of San Xavier and Purisima Concepción--churches were ostensibly following the same plan.
The Spanish Empire imposed all sorts of empire-wide rules, but away from the central authorities, rules could be broken. Up on the remote northern frontier, "isolation gave rise to ingenious approaches to design, construction and decoration."
Sometimes built as mere chapels for rough forts, the northern churches are more modest than the ornate colonial basilicas in wealthy cities to the south. But Giffords agilely makes the case that their relative simplicity is a virtue: "(T)he simpler churches in early settlements and missions of northern New Spain ... often tell the observer far more about arrangement of space, proportion and construction than do the churches to the south, for all their polychrome, gilding, swirls and angles."
Nearly all of the churches are immediately recognizable as hot-climate architecture, with thick adobe walls and covered porticoes borrowed from Spain and, before that, from North Africa. Some elements are also lifted from Native American architectural adaptations to the desert, particularly in New Mexico, where Spanish conquistadors and indigenous people had "to solve similar problems of defense, heat and light."
The mission churches typically follow a standard Catholic cruciform floor plan. But a cornucopia of decorative styles, from the Gothic to the Baroque to the Rococo, help give each church its own distinctive charm. Their heavily ornamented surfaces--from the leaping cat on the San Xavier façade to its faux painted tiles inside--betray the horror vacui, or "fear of emptiness," that marks the lively mission aesthetic.
In the New World's creative cultural collision, the styles merged into something new. Sonora's San Pedro y San Pablo de Tubutama is a beguiling example of what Giffords calls the mestizo style. A rhythmic array of disks and spirals, carved and molded in whitewashed plaster, unspools across Tubutama's façade.
At 480 pages, this hardbound book--enhanced with black-and-white photos and floor-plan drawings--is not meant to be lugged along as a tour guidebook, but it will doubtless be the standard reference for years to come. Giffords occasionally gets mired in dense academic language, but once she gets to the chapters brimming with facts and details, she hits her authorial stride.
Embedded in her learned treatments of style are insights into mission life. The strange cylindrical structure out back of San José de Tumacacori near Tubac, for instance, may have been a charnel house--where "the body was allowed to decompose so that the bones might later be buried in a much smaller area."
"From the earliest years," she writes, "Indians were employed as sculptors, painters, carpenters." And with a note of pride understandable coming from the mother of Southern Arizona's congresswoman, she reveals that it may well have been women who slapped together the adobe bricks that made these missions possible.