Sweet Grass County is a county located in the U.S. state of Montana. As of the 2020 census, the population was 3,678. Its county seat is Big Timber. The county was founded in 1895.

Park County is a county in the U.S. state of Montana. At the 2020 census, the population was 17,191. Its county seat is Livingston. A small part of Yellowstone National Park is in the southern part of the county.