Complex sentence: On June 21,1861, the "Central Pacific Rail Road of California" was incorporated in California and its name was then changed to "Central Pacific Railroad of California" on October 8,1864, after the 1864 Pacific Railway Act amendment passed that summer.
Split into simpler sentences: On June 21,1861, the "Central Pacific Rail Road of California" was incorporated in California. On October 8,1864, its name was changed to "Central Pacific Railroad of California" after the 1864 Pacific Railway Act amendment passed that summer.