In the 1970s, three student teachers in Minnesota made an educational computer game based on the Oregon Trail. The goal of the game was to successfully travel the trail from Independence, Missouri to Oregon City, Oregon. Dangers of the trail included river crossings, illnesses, sick oxen, and hunger. Over the next two decades, new versions of the game were made that added more options and included better graphics. The second version included zombies and oxen. The goal was to survive as long as you can before you die.