Complex sentence: He spent about six years from 1850 to 1856 in Califonria and Western Arizona Ajo, Arizona and worked as an assayer in the mines near Yuma, Arizona Arizona City.
Split into simpler sentences: He spent about six years, from 1850 to 1856, in California and western Arizona. At Ajo, Arizona he worked as an assayer in the mines near Yuma and Arizona City.