Ten days before the battle, a band of roughly thirty American settlers had stormed into Sonoma, seized the town from Mexican authorities, and declared the California Republic. They raised a homemade flag featuring a grizzly bear so crude that onlookers initially mistook it for a pig. The rebels, who called themselves Osos -- Bears -- had no formal military backing, no supply lines, and no clear plan beyond asserting that California was no longer Mexico's to govern. What they did have was a grievance: rumors that the Mexican military commander, General Jose Castro, planned to expel American settlers from Alta California. Whether the rumors were true mattered less than the anxiety they produced. The Bear Flaggers needed gunpowder, and they needed it fast.

Around June 16, the rebels dispatched William Todd and a companion to Bodega Bay to collect powder from sympathetic American settlers. Two days later, Thomas Cowie and George Fowler set out for Rancho Sotoyome near present-day Healdsburg, where Moses Carson -- brother of the famous scout Kit Carson -- had a cache. Neither party returned on schedule. When Lieutenant Henry Ford sent Sergeant Gibson with four men to investigate, Gibson found the powder but also captured a Californio fighter who delivered grim news: Cowie and Fowler were dead, killed by irregulars under Juan Padilla and Jose Ramon Carrillo. Todd and his companion had been seized as well. Ford gathered his men and rode south, grief and fury sharpening their purpose.

Ford's militia found the enemy at Rancho Olompali, land that had been granted just three years earlier to Camilo Ynitia, a Coast Miwok chief -- one of very few Native Californians to hold a Mexican land grant. When Ford approached the adobe, men began pouring from the building. Captain Joaquin de la Torre had brought fifty soldiers north from the Presidio of Monterey and joined Padilla's irregulars, swelling the Mexican force to about seventy. Ford's men fell back to a grove of trees and waited. When the cavalry charged on horseback, the Americans opened fire, killing one rider and wounding another. What followed was a prolonged exchange at range, and here technology told the story: the Bears carried long rifles accurate at distances where Mexican muskets could not reach. An Alta California militiaman later admitted that their muskets simply could not shoot as far. During the confusion of this long-range standoff, Todd and his companion broke free from the house and sprinted to the American lines.

De la Torre's force disengaged and withdrew to San Rafael, having suffered several wounded. No Americans died. As skirmishes go, it was modest -- a few dozen shots exchanged over oak-dotted pastureland, one confirmed fatality, a prisoner rescue that succeeded almost by accident. Yet the Battle of Olompali was the only real combat of the Bear Flag Revolt, a rebellion that lasted just twenty-five days before the United States Navy arrived and folded California into the Mexican-American War already underway. The homemade bear flag came down, the Stars and Stripes went up, and the short-lived California Republic became a footnote absorbed by a much larger conflict. The Osos never had to fight again.

Today the site is Olompali State Historic Park, a quiet expanse of rolling grassland and coast live oaks along Highway 101 in Marin County. The ranch that Camilo Ynitia received -- and that briefly became a battlefield -- later passed through a succession of owners. In the 1960s, it housed a commune; before that, a Jesuit retreat. The Coast Miwok presence here stretches back thousands of years, far deeper than the brief morning in 1846 when American and Mexican forces collided on ground that belonged, in the most literal legal sense, to neither of them. Walking the trails now, visitors find reconstructed Miwok structures, the ruins of a Victorian-era ranch house, and very little to indicate that California's only revolutionary battle happened underfoot.