Ismay began as a Milwaukee station on O'Fallon Creek. One story is that it was named for Isabelle and Mary Peck, daughters of George W. Peck, general counsel for the railroad; however, elsewhere the names are given as Isabel and May Earling, daughters of another official. Ismay was on the old stage line that ran from Fort Lincoln at Bismark to Fort Keogh (now home to the Range Rider Museum in Miles City) 1878-83. The old trail came down the ravine in the north part of town and crossed O'Fallon Creek here. The town originated with the building of the Milwaukee Railroad in 1907.(from Cheney's Names on the Face of Montana, Mountain Press Publishing Company)
In May of 1993, the town of Ismay was contacted by a radio station in Kansas City, Missouri with a special request for the town to consider changing the name of the town to Joe, Montana for the duration of the football season. The radio station promoter felt that this was a great way to honor the NFL quarterback, Joe Montana who had recently been signed to the Kansas City Chiefs. Ismay, population 22, agreed. On July 3, 1993, it was official: Ismay became Joe. In celebration, the town organized a ranch rodeo, a parade, and a night show for July 3. The events drew over 2,000 spectators. They hoped to raise a couple thousand dollars to cover the annual operating cost of their volunteer fire department. The mayor, who earns $4 a month for his mayoral duties, proudly reported that by February of 1994, the town had netted nearly $70,000. The town's name has since reverted to Ismay.