"Thunder on the Sierra" could be classified as either a book about California ranchos or as a gold rush book. I decided on the "rancho" era because the main character, Mateo, is a California boy of Mexican heritage known as a "Californio". Author Kathy Balmes loosely based this first-person historical fiction novel on the writings of Ignacio Villegas, who wrote "Boyhood Days Reminiscences of California in the 1850's". In this story, Mateo has just lost his father, a mayordomo of a big cattle ranch. When his prized horse is stolen by none other than the notorious Juaquin Murieta, Mateo vows to get him back. Mateo ends up working for a year as an "arriero", leading pack mules to the gold fields. 1852 is a turbulent time to be a Californio. The easier placer gold had already been discovered and Americans were leaving the mines and squatting on Californio rancho land. Even though the "Foreign Miner's Tax" of 1850 had been repealed, the "Land Act of 1851" had been passed. Californios now had only two years to prove they owned their land. Balmes wove these historical occurrences into her story of Mateo. (This was done usually in a natural manner, but sometimes a little too obviously.) "Thunder on the Sierra" is part of the "Adventure in America" series. Vickie Catapano's black and white drawings display good details of the California topography and clothing of the era. ( )