Boulder River (Sweet Grass County, Montana)

The Boulder River ( formerly also a Cross Rivers or Rivers or Rivers across -across ) is a fast-flowing mountain river of medium size in the southern U.S. state of Montana.

It rises in the Absaroka Beartooth Wilderness Area, on the northern edge of Yellowstone National Park and flows near the town of Big Timber in the Yellowstone River.

Another river called Boulder River is located in the southwest of the State of Montana, this flows into the Jefferson River.