Running a marathon is no easy feat and participating in an Ultramarathon is only for the most skilled and prepared. However, there are some Ultramarathons that take the cake when it comes to distance, terrain, temperature, and duration. These grueling courses have the ability to take out some of the world’s greatest long distant runners, and those who finish have something to remember for the rest of their lives. We reviewed some of the most daring, toughest, and longest Ultramarathons that the United States has to offer. We also discuss what you can expect if you decide to participate in any of these events. For some of these courses, your legs might feel sore just from reading about them.