Miles City is the old cattle town of eastern Montana, set where the Tongue River meets the Yellowstone. It still feels tied to ranching, railroads, auctions, rodeo, and the long distances of the northern plains.
The city is worth a spare day if you are already crossing eastern Montana and want something more rooted than a fuel stop. Range Riders Museum is the headline, with enough cowboy, military, Native American, and pioneer material to make the town's history tangible. Downtown adds brick storefronts and a working small-city feel, while WaterWorks Art Museum gives the place a more unexpected cultural stop.
Do not expect a polished resort town. Miles City is best approached as a plains-history stop with a few strong anchors and a lot of space around it.