Complex sentence: The Chattanooga and Durham Railroad was formed in 1894 from the failed Chickamauga and Durham Railroad which had built a railroad between Chickamauga, GA and Durham, GA to haul coal from Lookout Mountain, Georgia.
Split into simpler sentences: The Chattanooga and Durham Railroad was formed in 1894 from the failed Chickamauga and Durham Railroad. The latter had built a railroad between Chickamauga, GA and Durham, GA to haul coal from Lookout Mountain, Georgia.