Hennessy's history began when "Copper King" Marcus Daly, a powerful businessman from Butte, Montana, had a falling out with his business associate in Missoula, Montana, A.B. Hammond. Daly decided that Butte needed a store that would compete with Hammond's Missoula Mercantile to sell goods to miners in Butte and lumbermen in Missoula. He found fellow businessman, Danel Hennessy. Hennessy owned and operated a successful store in Butte. With the clout of financial backing from Daly, Hennessy hired Frederick Kees, an architect from Minneapolis, to design one of Butte's most elegant buildings.
Hennessy's department store opened for business in 1898. Inside, shoppers encountered marble staircases, oak counters, and solid bronze balustrades. Customers found every type of merchandise in 17 different departments from the basement level, up through the first three floors. At its opening, the Butte Hennessy's store employed 200 people.
Hennessy's stores expanded from Butte into locations in Missoula, Billings, and Helena. The chain was acquired by Mercantile Stores in the 1970s and headquarters moved to Billings in 1980. The Hennessy's chain closed the Butte store in February 1980 after years of difficult business. In 1998 Dillard's acquired Mercantile Stores and the Hennessy's brand was dropped in favor of Dillard's. At this time Hennessy's operated three stores in Helena, Billings, and Missoula.