Jay Em Historic District, Historic district in Goshen County, Wyoming, United States.

Jay Em Historic District preserves the abandoned center of a town Lake Harris laid out on Rawhide Creek from 1912. Its contributing structures include a 2½-story gambrel-roofed restaurant-feed store-post office-general store, a concrete-block lumber yard with false front and rear warehouse, a brick stone company building with fifteen windows, a small frame bank, a drive-through gas station, a repair garage with globe finials, a water tower now 60 feet tall without its tank, and Harris's house built over the original dugout with an owl wall.

Jay Em grew from Jim Moore's 1860s claim at a Texas Trail watering hole, the last before Lusk; his "J Rolling M" brand named Jay Em Creek. In 1905 Silas Harris and his sons took over the Jay Em Cattle Company, and Lake Harris filed a homestead claim on Rawhide Creek in 1912, building a house, then a feed store that held the post office from 1915. A weekly newspaper ran 1917–1921, a bank followed in 1920, and decline came after the 1930s.

The name Jay Em comes from Jim Moore's "J Rolling M" cattle brand, which also gave Jay Em Creek its name. The weekly Jay Em Sentinel and Fort Laramie News, edited by Lake Harris with a circulation of 300, ran from 1917 to 1921. The general store served the surrounding ranchers until the late 1970s.

Visitors should arrange tours in advance by contacting Hazel Mudgett at (307) 322-2839 to access the site. The unpaved roads and lack of modern features like sidewalks mean sturdy footwear is helpful for exploring the grounds comfortably.

The water tower survives as a 60-foot (18 m) structure with its tank missing, and Lake Harris's house was built over the original dugout, where an "owl wall" is still visible. The lumber yard pairs a 2½-story false-fronted concrete-block sales building with a wood-frame warehouse across a courtyard.