Complex sentence: Jim Savage or James D. Savage, (1817--1852), California pioneer, 49er, businessman, American soldier in the Mexican American War, and commander of the California Militia, Mariposa Battalion in the Mariposa War, discoverer of the Yosemite Valley.
Split into simpler sentences: Jim Savage or James D. Savage, (1817--1852) was a California pioneer. He was a 49er, businessman, American soldier in the Mexican American War, and commander of the California Militia, Mariposa Battalion in the Mariposa War, and the discoverer of the Yosemite Valley.