Question: Jackson is what south of a small town in Beaverhead County, Montana, United States?

Context paragraphs:
Ruby River: The Ruby River is a tributary of the Beaverhead River, approximately 76 mi (122 km) long, in southwestern Montana in the United States.  It rises in the Beaverhead National Forest in southwestern Madison County between the Snowcrest Range and the Gravelly Range.  It flows north through the Ruby River Reservoir, past Alder, then northwest, flowing between the Tobacco Root Mountains to the northeast and the Ruby Range to the southwest.  It joins the Beaverhead near Twin Bridges.  The Beaverhead becomes the Jefferson River 2 mi (3.2 km) downstream where it joins the Big Hole River.

Wisdom, Montana: Wisdom is a small town in Beaverhead County, Montana, United States.  The population was 98 at the 2010 census.  The ZIP Code of the area is 59761.  The town includes three tourist lodgings, service station, grocery, school (K-8), post office and a Forestry Service office.  It is also included within the boundaries of the Wisdom, Montana, Census Designated Place, which is named after the town.

Bannack, Montana: Bannack is a ghost town in Beaverhead County, Montana, United States, located on Grasshopper Creek, approximately 11 mi upstream from where Grasshopper Creek joins with the Beaverhead River south of Dillon.  Founded in 1862, the town contemporarily operates as a National Historic Landmark and is managed by the state of Montana as Bannack State Park.

Wise River: The Wise River is a tributary of the Big Hole River, approximately 30 mi (48 km) long, in southwestern Montana in the United States.  It rises in the Beaverhead National Forest in the Pioneer Mountains in Beaverhead County.  It flows NNW through the mountains and joins the Big Hole near the town of Wise River.  The river has also been known as Elkhorn Creek.

Armstead, Montana: Armstead is a former community in Beaverhead County, Montana, United States, about 21 mi south of the county seat of Dillon.  It was named after miner Harry Armstead.  Armstead was located in a narrow valley of the Beaverhead River, near the mouth of Horse Prairie Creek.  The town was a station stop on the Union Pacific Railroad line from Idaho Falls, Idaho to Butte, Montana.  There was a post office in Armstead from 1907 to 1962.

Rocky Hills: The Rocky Hills, el.  6916 ft , is a small mountain range south of Bannack, Montana in Beaverhead County, Montana.

Clark Canyon Dam: Clark Canyon Dam is an earthfill dam located in Beaverhead County, Montana, about 20 miles (30 km) south of the county seat of Dillon.  The dam impounds the waters of the Beaverhead River, creating a body of water known as Clark Canyon Reservoir.  The structure was constructed in 1961-1964 by the United States Bureau of Reclamation, to hold water for downstream irrigation and for flood-control purposes.

Beaverhead County High School: Beaverhead County High School is a high school in the small town of Dillon, Beaverhead County, Montana.

Jackson, Montana: Jackson is an unincorporated community in Beaverhead County, Montana, United States.  Although it is unincorporated, Jackson has a post office with a ZIP code of 59736.  Jackson lies on Montana Secondary Highway 278 south of Wisdom and northwest of Dillon.

Chief Joseph Pass: Chief Joseph Pass el.  7251 ft is a mountain pass on the continental divide of the Rocky Mountains in the northwestern United States.  It separates Lemhi County, Idaho and Beaverhead County, Montana.  The pass is in the Bitterroot Mountains and is traversed by Montana State Highway 43.  The pass is named after Chief Joseph of the Wallowa band of the Nez Perce tribe who traversed the pass in 1877 during the Nez Perce War.

Supporting paragraphs: Jackson, Montana Wisdom, Montana
Answer: unincorporated community