Complex sentence: California Central Railway expanded and completed line started by the Riverside, Santa Ana and Los Angeles Railway Co. line completed from Santa Ann to Los Angeles August 12,1888,34 miles and High Grove to Orange on Sept.15,1887,41 miles.
Split into simpler sentences: California Central Railway expanded and completed the rail line started by the Riverside, Santa Ana and Los Angeles Railway Company, from Santa Ann to Los Angeles on August 12,1888,34 miles. Also completed was he line from High Grove to Orange on Sept.15,1887,41 miles.