Who is Marquis de Mores from Mornings on Horseback and what is their importance?

The Marquis de Mores founded the town of Medora in the Bad Lands. He is described as a tall, spare and fit man, who was a superb horseman and a crack shot. The Marquis opened the first meat packing plant in the Bad Lands, and he butchered cattle on the range before transporting the meat east.