The Arboretum used to be a USDA Experimental Station to study the hardiness of trees, fruits and vegetables on the High Plains. The station operated from the 1930s until the early 1970s. It was not maintained (or irrigated!) until the early 2000’s. Starting in 2015, an apple orchard is being replanted on the site.
I visited to see the hardy fruit tree varieties, particularly the remaining trees from the original orchard planting.
It is located west of Cheyenne, just a few miles north of I-80 at ~6200’ altitude. This is what the nearby land looks like
Info about the apple orchard
It is a challenging place to grow trees, even more challenging than the front range of Colorado. This sign neglects to mention grasshoppers 
The new orchard. Note the windmill in the background. The healthiest looking varieties to my eye were Wealthy, Sweet 16, Harelred, MacIntosh and Summer Rambo.
From the old orchard. These trees are hardy! Almost 100 years old, surviving in Cheyenne, and with no care or water for several decades. The only old apple trees were crab apples, and some of these were bearing fruit.
Surprisingly, some of the healthiest looking old trees were apricots… Manchurian varieties, which are not known for fruit quality. They was no evidence of fruit from this season.
If you are interested in more details, I got this book from the library. There is a chapter on the research station and some interesting photos of the early days. It has quite a bit of history on early horticulture in Nebraska, Wyoming and Colorado.
It was interesting to see and it’s worth a visit if you’re in the area. There was little fruit to be seen, however. The trees are surviving, but not thriving. Growing fruit on the high plains is tough. Probably a better hobby than a business.