From the record
“The Jay Em Historic District comprises the abandoned center of the village of Jay Em, Wyoming. The town was planned and established by Lake Harris between 1912 and 1915 as a service town supporting ranchers in the surrounding area.”
Wikipedia article Jay Em Historic District, CC BY-SA 4.0.
One of 7 National Register listings published here for Goshen County · listed in 1984 · category: District.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service