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The Refugio Valley

The San Francisco Bay region is located at a convergent boundary of tectonic plates. Its hills, valleys and waters were shaped by the collision of the North American and Pacific plates, which were driven by plutonic forces deep in the Earth 28 million years ago. 

Forty per cent of all California’s surface waters flow through the Carquinez Strait and San Pablo Bay. San Pablo Bay is part of the San Francisco Bay Estuary, the largest on the Pacific Coast of the Americas. It reached its current size about 12,000 years ago due to sea level rise. Previously a river valley, it was filled as the Ice Age glaciers melted.  A mighty river had flowed through the valley from Carquinez to the Golden Gate from 620,000  years ago, when a wall of water from an ancient inland lake broke through the gap between today’s Crockett and Benicia. Then, the Pacific Ocean surface was 500 feet lower than today. 

The town of Pinole is among the earliest European-settled places in California. It took shape as an agricultural port during the span of Mexican Alta California. With a Spanish land grant in 1823, it began as the Martinez family ranch engaging in the California commerce of the time: trading cattle, hides, tallow and produce for finished goods in sail-powered oceanic trade. 

Leading up to 1878, the new people of Pinole were Americans; the old people were descendants of the Mexican or Spanish settlers. Pinole had been transformed by the Americans arriving in the Gold Rush of 1848 and after California statehood in 1850. 

Sunset behind Mount Tamalpais over San Pablo Bay