Question: The Boulder River and the Jefferson River are tributaries in which state?

Context paragraphs:
Beaverhead River: The Beaverhead River is an approximately 69 mi tributary of the Jefferson River in southwest Montana (east of the Continental Divide).  It drains an area of roughly 4778 mi2 .  The river's original headwaters, formed by the confluence of the Red Rock River and Horse Prairie Creek, are now flooded under Clark Canyon Reservoir, which also floods the first 6 mi of the river.  The Beaverhead then flows through a broad valley northward to join the Big Hole River and form the Jefferson River.  With the Red Rock River included in its length, the river stretches another 70 mi , for a total length of 139 mi , one of the more significant drainages of south-western Montana.

Montana Highway 69: Montana Highway 69 (MT 69) is a route running northerly from an intersection with MT 55 in the community of Whitehall.  The highway extends approximately 38 mi to an intersection with Interstate 15 (I-15) at the northern edge of the town of Boulder.  Most of the route follows the Boulder River valley, a scenic and relatively unspoiled rural landscape.

Basin, Montana: Basin is a census-designated place (CDP) in Jefferson County, Montana, United States.  It lies about 10 mi southeast of the Continental Divide in a high narrow canyon along Interstate 15 about halfway between Butte and Helena.  Basin Creek flows roughly north to south through Basin and enters the Boulder River on the settlement's south side.  The population was 255 at the 2000 census.

Jefferson River: The Jefferson River is a tributary of the Missouri River, approximately 83 mi long, in the U.S. state of Montana.  The Jefferson River and the Madison River form the official beginning of the Missouri at Missouri Headwaters State Park near Three Forks.  It is joined 0.6 mi downstream (northeast) by the Gallatin.

Boulder, Montana: Boulder is a town in and the county seat of Jefferson County, Montana, United States.  It is on the north bank of the Boulder River between Butte and Helena, slightly east of the Continental Divide, at the intersection of Interstate 15 and Montana Highway 69.  The population was 1,183 at the 2010 census.  It is part of the Helena Micropolitan Statistical Area.

Boulder River (southwestern Montana): The Boulder River is a 77 mi tributary of the Jefferson River in southwestern Montana in the United States.

Red Rock River (Montana): The Red Rock River is a roughly 70 mi river in southwestern Montana in the United States.  Its drainage basin covers over 1548 mi2 .  Its furthest tributary, Hell Roaring Creek, originates in the Beaverhead National Forest within a few hundred meters of the North American Continental Divide and Montana-Idaho border near Brower's Spring, at an elevation of about 9100 ft .  Brower's Spring is near the furthest headwaters of the Missouri River, one of the major watercourses of the central United States.  The drainage flows north and west with its name changing to "Red Rock Creek" into the Red Rock Lakes in the middle of a wide grassy valley; the Red Rock River issues from the west side of Lower Red Rock Lake.  It flows west, receiving many tributaries such as Peet Creek and Long Creek, widening into the Lima Reservoir and then passing through a canyon, which ends near Lima, Montana.  From there, it flows northwest through a valley, passing Kidd and Red Rock, and into Clark Canyon Reservoir.  Under the waters of the lake was once the confluence of the Red Rock and Horse Prairie Creek, forming the Beaverhead River, a tributary of the Jefferson River, in turn a headwater of the Missouri River.

Boulder River (Sweet Grass County, Montana): The Boulder River is a tributary of the Yellowstone River, approximately 60 mi (96 km) long, in south central Montana in the United States.  It is one of two rivers named the Boulder River in Montana.

Feature Show Falls: Feature Show Falls is a waterfall on an unnamed tributary of the Boulder River in Washington, United States.  It is a segmented 180 ft drop that is about 35 ft wide at its base.  The falls drop directly into the Boulder River.

Table Mountain (Madison County, Montana): Table Mountain, el.  10213 ft is the highest peak in the Highland Mountains in Madison County, Montana.  It is located in Beaverhead-Deerlodge National Forest.  Headwaters of Moose Creek, Fish Creek and Hell's Canyon Creek, all significant tributaries of the Jefferson River flow off the face of the mountain.

Supporting paragraphs: Boulder River (southwestern Montana) Jefferson River
Answer: Montana