Complex sentence: Thomas William O'Brien (March 8,1862-August 24,1916) was a Klondike gold rush entrepreneur who was best known for his Klondike Mines Railway and Klondike Brewery businesses.
Split into simpler sentences: Thomas William O'Brien (March 8,1862-August 24,1916). Was a Klondike gold rush entrepreneur who was best known for his Klondike Mines Railway and Klondike Brewery businesses.