 Basque immigration peaked after the Spanish Carlist Wars in the 1830s—Ebro customs relocated to the Pyrenees—and in the 1860s following the discovery of gold in the foothills of the Sierra Nevada mountain range of California.The current day descendants of Basque immigrants remain most notably in this area and across the Sierras into the neighboring area of northern Nevada, then northward, into Idaho.When the present-day states of California, Arizona and New Mexico were annexed by the United States after the Mexican–American War (1848), there were reportedly thousands of Basques of Spanish or mixed Mexican origin living in the Pacific Northwest.