Even as golf continues to recognize the importance of fun and playability in course design, the measure of championship-caliber golf is still a course’s Resistance to Scoring. How does a course defend par? And is it fair? These courses embody that measurement. Resistance to Scoring is one of seven criteria we asked our 1,100 Golf Digest course-ranking panelists in the United States and Canada to evaluate in helping us determine our latest America’s 100 Greatest rankings. Using those same evaluations, we’ve determined our 20 Hardest Golf Courses in the United States. By definition, these are courses with the highest measure of difficulty -- while still being fair -- for a scratch player from the back set of tees. For some of us, playing these courses every day would beat up our egos. But to play some of golf’s classic designs, the right mentality is just to just enjoy the loop. Otherwise, judging by these comments from our course-ranking panelists, you might be in for a long day. —Stephen Hennessey