Complex sentence: At the age of fourteen, Van Horne began working on railroads serving in various capacities on the Illinois Central Railroad until 1864, then for the Chicago and Alton Railway for whom he served as the general superintendent from 1878-1879.
Split into simpler sentences: At the age of fourteen, Van Horne began working on railroads, serving in various capacities on the Illinois Central Railroad until 1864. He went on to work for the Chicago and Alton Railway, serving as general superintendent from 1878-1879.