[2] Jay Em is located on the old Texas Trail, running north–south through Goshen County, and featured the last watering hole before reaching Lusk.

By 1869, Moore had the second largest cattle ranch in the Wyoming Territory, under the brand "J Rolling M", leading to the naming of a small drainage "Jay Em Creek".

One of his sons, Lake Harris, established a post office in the Jay Em Ranch's bunkhouse, bringing the mail from Rawhide Buttes.

A newspaper, the weekly Jay Em Sentinel and Fort Laramie News (circulation 300), inevitably edited by Lake Harris, ran from 1917 to 1921.

The few remaining residents of Jay Em have moved to more modern accommodations scattered around the edge of town, leaving the center vacant.