Taylor Sheridan is already developing prequel series Y: 1883. Now he's working on another spinoff titled 6666, focusing on the Four Sixes ranch in West Texas. "Still operating as it did two centuries before when the Comanches still ruled the land, the 6666 is where the rule of law and the laws of nature merge in a place where the most dangerous thing one does is the next thing," per EW. "The Four Sixes is known for raising the finest horses and livestock in the world, and ultimately where world-class cowboys are born and made." ALSO: Watch Sheridan discuss expanding the Yellowstone universe.