Around 500 B.C. Shoshonean-speaking people established settlements in the San Gabriel Valley. The Spanish called them Gabrielinos, after the mission, but most now prefer the name Tongva, and acorn meal from the valley's abundant live oaks was a staple of their diet. The first Europeans to visit the valley came with the Portola expedition of 1769, whose diarist, Father Juan Crespi, recorded much of what is known of early California. The Franciscans founded Mission San Gabriel Arcangel on September 8, 1771, and drew most of the Tongva into its agricultural life, and after Mexican independence in 1821 the mission lands were nationalized.
More about Duarte
On May 10, 1841, Governor Juan Bautista Alvarado granted nearly 7,000 acres in the central and northern San Gabriel Valley to the former Mexican corporal Andres Avelino Duarte and his wife, who named it Rancho Azusa de Duarte. Azusa comes from Asuksa-gna, "skunk place," the name of a Tongva settlement in the foothills. The grant now covers parts of Arcadia, Monrovia, Irwindale, Azusa and Baldwin Park and all of Bradbury and Duarte. Duarte had local Native people build a small house for his family and plant a garden and orchards near the springs in today's Fish Canyon.
After the United States took California in 1848 and Congress created a land commission in 1851 to review Spanish and Mexican grants, Duarte ran up legal and other debts and sold parts of the rancho. The first sale, 225 acres at its southern end, went to Michael Whistler, who later sold it to Dr. Nehemiah Beardslee, founder of Duarte's first school, which bears his name.
Sources
Wikipedia: Duarte, California