While playing tour guide to summer visitors, Sonoma County people might - but probably don't very often - cruise past the historically priceless though neglected and overgrown Carrillo Adobe on Santa Rosa's Montgomery Drive.
Locals might tell their guests during a drive-by that the crumbly earthen ruins behind the weeds and beneath a carport-type roof are what remains of Santa Rosa's beginnings, its first permanent, non-native residence.
That description is not inaccurate, but a descendent of the founding Carrillos is part of a small corps of people excited and intrigued by evidence that the site of the forlorn, fenced-off adobe was conceived as something immensely more consequential than the ranch home of a family of settlers.
"It looks like there was much more intent there," enthused Larry Carrillo, a Santa Rosa businessman who's dedicated much of his 67 years to preserving and promoting the historical site.
He's fascinated by research suggesting his ancestors in the clan of Maria Ygnacia L?ez de Carrillo did not build the 1837-38 adobe ranchhouse from scratch but erected it partly atop stout, stone foundations that were placed earlier, evidently with a much more substantial building in mind.
A Petaluma archeologist, William Roop, discovered the footings during 2006 excavations required by a developer's proposal to build 140 condominiums on 15 acres that stretch along Santa Rosa Creek and Montgomery Drive from the adobe west to St. Eugene's Cathedral.
To Roop, the origins of the heavy-duty foundation beneath the Carrillo Adobe are clear. He's convinced they were placed by laborers on the orders of Franciscan priests intent on building in Santa Rosa the 22nd and northernmost California mission.
If true, this would mean the place where Santa Rosa was born is the exact spot at which the colonial quest to hold and tame California through a string of missions died.
"We have some riddles here," Larry Carrillo said. He holds that the discovery of the footings and the prospect they were intended to support a mission increase the urgency for Santa Rosa to preserve and highlight at least part of the adobe as a historical treasure.
It's not a new idea that the Franciscans who founded the 20th mission in San Rafael in 1822 and the 21st in Sonoma in 1823 planned also to build a mission in Santa Rosa no later than about 1829 - nearly a decade before the arrival of Maria Carrillo, widowed mother-in-law of Gen. Mariano Vallejo, one of the most powerful men in what was then Mexico's California.
But prior to the discovery of the foundation footings, it was unknown just how close Santa Rosa came to having a mission or exactly where it would have been located.
The historical record of the land near what Maria Carrillo called Rancho Cabeza de Santa Rosa includes accounts of Franciscans from Mission San Rafael Arcangel creating a small outpost or "asistencia" there for converting local Pomos.
"This was definitely trying to become a mission," said Roop, the consulting archeologist. His research leads him to believe the Franciscans did commence construction of an envisioned Mission de Santa Rosa de Lima but abandoned the project before completion of the stone foundation.
"We think what scared them off was the Pomo-Wappo war of 1829 up in Alexander Valley," Roop said.
Whatever forces might have deterred the Franciscans from founding a mission in Santa Rosa, Roop believes the stone footings he and his crew discovered beneath and beside the Carrillo Adobe were intended to support that mission.
"The magnitude of the footings argues that was possibly the selected site for a church building associated with the planned, but never completed, Mission de Santa Rosa de Lima," Roops' report said.
In addition to the massive foundation beneath a portion of the adobe's remains, the team also found footings that were never built upon, suggesting the L-shaped ranch home was planned to have at least three sides.
What is left above ground at the Carrillo Adobe are the remains of what's been called the East Wing. The North Wing collapsed decades ago. Roop's report said the buried footings for what would have been the South Wing further suggest that whoever laid the foundation was intending to build more than a ranchhouse.
Eric Stanley, a historian in Santa Rosa who contributed to the archeological report, views the mission scenario as just one plausible explanation for the existence of the adobe's outsized and surplus footings.
"There are several possibilities sitting there," said Stanley, curator of history for the Sonoma County Museum. He considers it possible that General Vallejo himself had construction begun on a mission or similar structure that would help him secure the Santa Rosa portion of the frontier.
If it was Vallejo's project, Stanley said, it might be that he quit because he ran out of money for it.
"A lot of it still remains a mystery," Stanley said.
Whoever began a significant project at the site of what would become the Carrillo Adobe, he said, "it seems perfectly clear they didn't get beyond the footings of whatever they were building."
Stanley worked with Roop's firm, Archaeological Resource Service, on a dig and historical research project as part of Santa Rosa City Hall's consideration, nearly six years ago, of the most recent development plan for that swath of creekside property along Montgomery Drive.
Barry Swenson Builders of San Jose proposed to build 140 condominiums on the site. The City Council approved the project, which included plans for a two-acre, low-maintenance community historical park around the Carrillo Adobe.
But ground was never broken for the envisioned Creekside Village.
"We still own the property and are just waiting through the tough economic time," said Mike Black, project manager with Barry Swenson Builders. When the condos are built, the project will include the two-acre Carrillo Adobe park, he said.
For Larry Carrillo and the Friends of the Carrillo Adobe, the discovery of the stone footings makes the adobe all the more intriguing and the necessity of preserving it all the more pressing. When and if a development plan is reactivated, Carrillo said, he'll do whatever he can to assure nothing is built over the top of the previously unknown footings.
Carrillo is enchanted by the questions that remain about exactly what the layers of the foundation intended to build, what foiled their plans and what the Carrillos and Vallejos knew or didn't know about the stones that evidently were in the ground when they began construction of Santa Rosa's first non-native house.
For the present, Carrillo said, "We're not talking about whether to develop or not. The question is, what happened there?"
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