There are many web pages out there that claim that Colorado has 75% of the land over 10000 feet in the US. Let's examine this claim.
In The Average Elevation of the United States, published in 1894, Henry Gannett reported these areas:
Gannett's report gives the square miles. The percentages are computed from the areas he reported. On the maps available at that time, he found no considerable areas over 8000 feet in Washington and no considerable areas over 9000 feet in Idaho, Nevada, and Oregon. He found no extended areas over 10000 feet in Montana and Arizona. Alaska and Hawaii, of course, were not included. They did not gain statehood until the 1959. As a matter of fact, Utah, Arizona, and New Mexico were not states in 1894, but Gannett did consider them.
Fast forward to the twenty-first century. Alaska and Hawaii are now added to the total. This has the effect of reducing Colorado's percentage of the overall total. The National Atlas profile of the U.S. gives an area of 20230 square miles above 10000 feet. How is this distributed among the 13 states involved? Finding no information on the breakdown more recent than Henry Gannett's nineteenth-century results, I made map measurements of more than 900 closed 10000-foot contours comprising more than 97% of those 20320 square miles. Following are the results of these measurements:
Notice that Henry Gannett's identification of the top five states by area > 10000 feet holds true to this day! We can also see that despite having hundreds of web pages stating that Colorado contains 75% of the land area of the U.S. with an altitude over 10000 feet, an accurate statement would say something like "Colorado has more than half of the land in the U.S. with an altitude over 10000 feet." instead.
I consider the myth that Colorado contains three fourths of the land in the United States above 10000 feet to be debunked. Henry Gannett, known as the father of government map making, was closer to the mark more than a century ago. We have information being disseminated by twenty-first-century technology that is of lower quality than information that was available in the nineteenth century.
Realistic statements on Colorado's terrain topping ten thousand feet
Colorado has about 56% of the U.S. land area above 10000 feet. This means that Colorado contains more land area over 10000 feet than all the other states combined. Colorado has more than 11000 square miles of terrain higher than 10000 feet above sea level, an area larger than Maryland.