New Idria also has a rich tradition of Spanish and Mexican settlements, many predating California statehood. Several Spanish explorers settled in this area and their descendants still live in the surrounding region. A few of these family names are:
- Castro—Today's local Castro families are descended from Joaquín Isidro de Castro, who arrived in this area with the Anza expedition. His grandson, General José Castro became the Governor of Mexico's California from 1835 to 1838. The Castro family name is on the historic Castro Adobe in Santa Cruz County and the San Juan Bautista Castro adobe, now know as the Breen Adobe (California Historic Landmark 179). The adobe was sold to Patrick Breen, a survivor of the ill-fated 1846 Donner party.
- Larios—José María Larios (born 1738) came from Malaga, Spain. He settled in San José in 1791 and later moved to Las Aromas near San Juan Bautista where he died in 1818. The family name (misspelled as "Larious" by map makers) is still visible in the names of Larious Canyon, Larious Creek, and Larious Spring. Larious Spring is the homestead site of José Larios (grandson of José from Spain and son of Manuel Larios and María Pacheco). José's father, Manuel, received the Spanish land grant, Rancho Santa Ana y Quien Sabe. José married Juana Castro (daughter of General José Castro).
- Cantua—Ygnacio Cantua was another settler was one of the original settlers in San Juan Bautista. He came to Alta California as a solder with the first Anza expedition. His son, Guadalupe, lead Spanish exploration into the San Joaquín Valley to gather native Californians to the San Juan Bautista Mission. Cantua Creek, located just over the hill from New Idria and made famous by Joaquín Murrieta, is named for Guadalupe Cantua. Two of Guadalupe's sons were members of Joaquín Murrieta's band. His daughter, Maria Guadalupe Cantua married Jose Hermenegildo Vásquez and their son was Tiburcio Vásquez, another famous California bandit.
- Chavoya—The Chavoya family is descended from Marcos Chaboya who was among the pioneer settlers of San Francisco. His son, Luis, operated California's first mine, "Chaboya's Mine" in 1825. The name of Chaboya's Mine was changed in 1848 to the New Almaden Quicksilver Mine. New Almaden Quicksilver Mine soon became the largest quicksilver mine in the Americas. The New Almaden mine is now the Almaden Quicksilver County Park in Santa Clara County. One of the Chavoya descendents was a miner at New Idria. Later, the Chavoya family became successful cattle ranchers in the area, until they donated all of their holdings to Mariana la Loca, a local cult leader of the time.
- Gonzales—José Manuel Gonzales also accompanied the Anza expedition. His grandson settled at Idria and opened the Gonzales saloon on the road just below Idria.
- Vásquez—Juan Atanasio Vásquez was among the Anza pioneers and his descendants settled in the Monterey and Idria area. His grandson, Larenzo Vásquez lived at Sweet Water Spring at the head of the Larenzo Vásquez Canyon. Larenzo was the uncle of Tiburcio Vásquez (some say, his brother).
Other pioneer family names connected with the New Idria region are: Ashurst, Bray, Tully, Frusetta, Akres, Chambers, Nuñez, Duckworth, Garcia, Hernandez, Williams, and Wright, to name a few.
