The annual, this time the 35th Annual, Monument Valley Iris Show will be May 30th and 31st, 2015 at the University of Nebraska Panhandle Research and Extension Center, a mile north of Scottsbluff on Hwy 71. Judging will be concluded by noon Saturday and exhibits will be open to public viewing at 1 p.m. until 5 p.m. and viewing will be 10 a.m. until 4 p.m. Sunday, May 31.
You can see all the details in the Star-Herald here.
This is also the location of the Monument Valley Iris Society Collection, which includes about 600 varieties of miniature dwarf, standard dwarf, intermediate and border bearded, miniature tall and tall bearded as well as several arilbreds and beardless irises. You can see many of these irises in bloom there now.