In 1835, Mexican Governor José Figueroa formally granted land in the Nicasio area to the Coast Miwok of Marin County, but the grant carried no legal weight that American courts would later recognize. By 1844, Governor Manuel Micheltorena had granted 56,621 acres, the largest single land grant in Marin, to Pablo de la Guerra and sea captain John B.R. Cooper. The Miwok filed their own claim with the Public Land Commission in 1852. It was rejected in 1855 for lack of documentation. About 500 Miwok had settled on the rancho; by 1850, they held just one league of land. The rest had been taken through what amounted to illegal confiscation, protested by the Indian residents and ignored by everyone else. The name Nicasio itself is believed to come from a local Miwok man baptized as Saint Nicasius by the mission padres, his original name lost to the colonial record.

The ownership history of Rancho Nicasio reads like a nineteenth-century legal thriller. By 1849, three men held the land: de la Guerra, Cooper, and the Irish surveyor Jasper O'Farrell. In 1850, de la Guerra sold his 30,848-acre share to Henry Wager Halleck, a young Army lieutenant who had arrived in California in 1847 alongside his friend William Tecumseh Sherman. Halleck hunted and fished along the creek near Nicasio that now bears his name, but his ambitions ran far beyond ranching. He became a partner in the San Francisco law firm Halleck, Peachy & Billings, and during the Civil War, Abraham Lincoln promoted him to general-in-chief of the armies of the United States. Meanwhile, Cooper sold his share to Benjamin Rush Buckelew, and O'Farrell sold his to James Black. Black eventually bought out Halleck's share too, along with the neighboring Rancho Olompali from Camilo Ynitia, the last Olompali Indian chief. Black's wife, Maria Agustina Sais, died in the dental chair of their son-in-law, Dr. Galen Burdell, in 1864. James Black himself died in 1870, the same year the federal patent was finally issued to the rancho's owners.

The Treaty of Guadalupe Hidalgo in 1848, ending the Mexican-American War, promised to honor existing land grants. In practice, honoring meant litigating. The Land Act of 1851 required every grant holder to prove their claim before the Public Land Commission, a process that took years and ruined many a Californio family who could not afford the legal fees. Rancho Nicasio's claim was filed in 1852 and not patented until 1870, nearly two decades of uncertainty during which the land changed hands repeatedly. A separate claim filed by former governor Juan Bautista Alvarado in 1853 was rejected for insufficient evidence. Each transaction generated its own layer of court documents, deeds, and surveys, preserved today in archives from Berkeley to Sacramento. The Miwok claim left almost no paper trail at all, which was precisely the problem.

Today, the village of Nicasio sits at the heart of what was once the rancho, a cluster of buildings so small that the 2020 census counted just 81 residents. The town square, listed on the National Register of Historic Places, centers on St. Mary's Church, built in 1867, and a baseball diamond where community games still unfold in summer. The rolling grasslands that surround the village look much as they did when the Miwok chose this land, golden in summer and startlingly green after the winter rains. The Rancho Nicasio restaurant, housed in a building from the 1800s, has become one of Marin's most celebrated gathering places, hosting live music on its patio while the hills darken around it. Thirty minutes from the Golden Gate Bridge, Nicasio operates at a pace that belongs to another century. The land that passed through so many hands has settled, at last, into a kind of quiet.