History of Mitsui Ranch and Sonoma Mountain Ranch Preservation Foundation
A Sacred Mountain
Coast Miwok had inhabited the area surrounding Sonoma Mountain for nearly 17 centuries by the time the first European explorers reached the Bay Area in the late 1700s. Based largely in what are now Marin and southern Sonoma Counties, the Coast Miwok led culturally rich, seasonally influenced lives, rotating among and inland from the marshlands at the coast. They intimately coexisted with the land and attributed fantastic, mythological origins to its features. To the Coast Miwok, Sonoma Mountain was Oona-pa’is. According to Arthur Dawson, historian at the Sonoma Ecology Center, this name probably translates to “Buckeye Mountain”, and its summit was said to have been “an island in the primordial ocean at the beginning of time.”
Miwok means “people” in all Miwokan languages. For more on the local history of the Coast Miwok, including efforts by the National Park Service to help descendants preserve and share their ancestral lands and stories, visit the NPS site.
But within two decades or so of the arrival of the Spanish in the Bay Area, many of the Native peoples (Coast Miwok to the north of the Golden Gate, Ohlone to the south) had been lured to the European missions for religious indoctrination and, unwittingly, lifetimes of forced labor. By 1810, the majority of the Native community had succumbed to European diseases—from smallpox to even the simplest of viruses—to which its people had no immunity. Abruptly, a centuries-old way of life disappeared and, with the indigenous peoples essentially extirpated, Europeans appropriated former Native lands surrounding the missions. Oona-pa’is was now in the hands of the Spanish.
After Mexico gained independence from Spain in 1821, the legendary Mariano G. Vallejo (soon to be Comandante General of California) acquired much of Sonoma Mountain in a land grant of 44,000 acres—quantified at that time as 10 leagues, and later increased by another five. Approximately 85 percent of the Foundation’s current geographic footprint falls within the boundaries of what became Vallejo’s “Rancho Petaluma.” (The town name, Petaluma, is a transliteration of the Coast Miwok phrase péta lúuma, which may mean hill backside, referring to Petaluma’s proximity to Sonoma Mountain.)
The “Price” of a Mountain
With the Treaty of Guadalupe Hidalgo, which in 1848 brought an official end to the Mexican-American War and ceded California to the United States, then-General Vallejo began selling parcels of Rancho Petaluma to settlers swarming into the state to join the rush for gold. Sales records date back to 1859, when John F. Fay of Sonoma County bought two parcels (most of the current Foundation property area) for $6.00 an acre—a sum of $3,280 for all 547 acres. The land continued to change private hands until 1902, when it sold to the William Hill Corporation of Petaluma, a banking firm that held more than 6,000 acres in Sonoma and Marin Counties. William Hill was also a stockholder and director of the Sonoma County Water Company, which held water rights to Copeland, Lynch, and Adobe Creeks, whose headwaters flow from the mountain. After 12 years of working its consolidated properties on the mountain, the company sold all corporate interests in the land to William’s son, Alexander B. Hill, in 1914. Just four years later the company unincorporated and the property was sold into a joint tenure. It remained family-owned (by the Offutts and Merritts, and then the Lowreys) until the current owner, Mary E. (Bonnie) Mitsui purchased the property in 1975.
A Modern Legacy of Preservation
In 1984, Bonnie Mitsui entered into a Conservation Easement agreement with The Nature Conservancy of California, preserving Mitsui Ranch from development in perpetuity. In 2012, Ms. Mitsui created the Sonoma Mountain Ranch Preservation Foundation, administered from headquarters in Ohio. The Foundation now works assiduously to restore, protect, and steward these 547 acres of grasslands, oak/bay laurel forest, riparian corridors, and their Native inhabitants.
To stay abreast of contemporary Coast Miwok efforts in Marin and Sonoma Counties, visit the website of the Miwok Archeological Preserve of Marin (MAPOM)
 Professor Gregory Sarris, Sonoma State University.
 From California Place Names: The Origin and Etymology of Current Geographical Names (second ed.) by E. G. Gustav and W. Bright (1998).