Black Mesa is a long flat-topped erosional remnant which runs from Oklahoma, through New Mexico, and into Colorado. Finding the correct GPS coordinates has been difficult. I found that the original coordinates given by lat-long.com were incorrect, placing Oklahoma's high point about 9 miles northwest in northern New Mexico . Moral of that story - zoom out first to make certain you are in the right state. Anyway the best coordinates I found are at 36°55.911'N, 102°59.842'W. and those are the ones used here. Here is the link I used to get them. There is a granite monument on the high point, so when you are actually there, you will be certain of the location.