Question: The St Regis River begins at Lookout Pass in which mountain pass on the Idaho/Montana border? 

Context paragraphs:
Lookout Pass: Lookout Pass is a mountain pass in the Rocky Mountains of the northwestern United States.  In the Coeur d'Alene Mountains of the Bitterroot Range, the pass is on the border between Idaho and Montana, traversed by Interstate 90 (formerly U.S. Route 10) at an elevation of 4710 ft above sea level.

Seok Pass: Seok Pass, Söök Pass or Suyak Pass (Russian: перевал Сёок , Kyrgyz: Сөөк ашуусу ) is a mountain pass in the Terskey Alatau mountain range of Kyrgyzstan.  Its elevation of 4028 m makes it the third highest mountain pass in Kyrgyzstan after Bedel Pass and Kyzylart Pass, and the highest one that is not on a border.  It connects the Ala-Bel plateau, where the Kumtor Gold Mine is located, to the upper Naryn River valley.

Raynolds Pass: Raynolds Pass, elevation 6844 ft , is a mountain pass on the Montana-Idaho border in the Rocky Mountains, United States.  The pass is on the Continental Divide, and is traversed by a state highway (Idaho State Highway 87 and Montana Highway 87).  The pass is named for Captain William F. Raynolds, an early explorer and officer-in-charge of the Raynolds Expedition of the Yellowstone region.  The pass is very gentle, with only a slight grade and no major hairpin curves to the highways connections with U.S. Route 287 in Montana and U.S. Route 20 in Idaho.

Elk Park Pass: Elk Park Pass, elevation 6352 ft , is a mountain pass on the Continental Divide in southwestern Montana, about 4 mi northeast of Butte.  It is traversed by Interstate 15 and is one of three crossings of the Divide by the Interstate (all in Montana), the others being Monida Pass (on the border with Idaho) and Deer Lodge Pass southwest of Butte.  Elk Park Pass lies on the border between Silver Bow and Jefferson counties and is remarkable for its highly asymmetrical nature.  The approach from the north is through namesake Elk Park, a high, mostly treeless plain (like South Park in Colorado or the Sierra Valley in California), and the grade is almost imperceptible.  The elevation at the northeast end of the park, about 10 mi from the pass, is about 6200 ft , only 152 ft lower than the pass itself.  However, at the south end, the highway drops 750 ft from the pass into Butte over a distance of only about 4 mi .

Keese Mill, New York: Keese Mill is a hamlet west of Paul Smiths, New York in Franklin County, New York in the Adirondacks.  It is named for a sawmill that was located on the Keese Mill dam on the Saint Regis River.  Keese Mills road, which starts at Paul Smiths, is the only road in the hamlet; it provides access to Black Pond and Long Pond, trails to Saint Regis and Jenkins Mountains and the Saint Regis Esker Trail, and the middle branch of the Saint Regis River.

Lookout Pass Ski and Recreation Area: Lookout Pass Ski and Recreation Area is a ski area in the western United States.  It is at Lookout Pass on Interstate 90, on the border of Idaho and Montana, 5 mi east of Mullan, Idaho.  It has a summit elevation of 5650 ft on Runt Mountain with a vertical drop of 1150 ft on the northeast-facing slopes.  Lookout Pass operates five days per week (closed Tuesday & Wednesday) during the ski season, and daily during the Christmas vacation break.

St. Regis River: The St. Regis River is an 86 mi river in northern New York in the United States.  It flows into the Saint Lawrence River at the hamlet of St Regis in the St. Regis Mohawk Reservation.  The Saint Regis River basin includes Upper and Lower St. Regis Lakes, and Saint Regis Pond in the Saint Regis Canoe Area.

Lewis and Clark Pass (Montana): Lewis and Clark Pass, el.  6424 ft is a mountain pass on the continental divide in Montana.  It lies at the head of the drainages of the west flowing Blackfoot River and the east flowing Dearborn River.  The pass is in the Helena National Forest in Lewis and Clark County.  The Continental Divide Trail traverses north and south through the pass.  At the time of the Lewis and Clark Expedition the pass was a much-used pathway where the native people living in what today is Montana crossed over the continental divide.  The pass was crossed by Meriwether Lewis on July 7, 1806, on the return leg of the Lewis and Clark Expedition with a party of nine men and his dog Seaman.  The pass was named for the expedition's two leaders–Lewis and William Clark.  Lewis and Clark Pass is the only roadless pass on the entire Lewis and Clark National Historic Trail.  It has gone from being one of the most used continental divide passes prior to the pioneer era to one of the least visited passes today.  It can be accessed by a 1.5 mi trail.  Visitors will encounter the pass much as Lewis did in 1806.  The furrows left by the countless dog and horse travois that crossed the pass are still visible (though fading) and this is one of the places along the expedition's route that visitors may still encounter a grizzly bear.  On a clear day, like Meriwether Lewis in 1806 one can see Square Butte in Cascade County, Montana, 40 mi to the northeast.

St. Regis River (Montana): The St. Regis River is an approximately 32.5 mi tributary of the Clark Fork of the Columbia River in Montana in the United States.  It begins at Lookout Pass on the Idaho/Montana border, flows east and ends at the confluence with the Clark Fork in the city of St. Regis.  Its drainage is 330 sqmi .  The record high flow for the St. Regis River in Montana was recorded on May 19, 1954 at 11,000 cubic feet per second according to USGS gaging data.

God Help Me Pass: The God Help Me Pass, or "Lekhalong-la-Molimo-Nthuse" in seSotho, is a mountain pass (elev.  2318 m) in western Lesotho.  It is the second mountain pass on the A3 road going into the central highlands.  The road ascends steeply from the village of Setibing, and near the summit is the Basotho Pony Trekking Centre, which offers a variety of trekking expeditions.  The Makhaleng River flows close by Setibing, and its valley forms the western approach to the pass.  The higher Blue Mountain Pass (2641 m), "Lekhalong-la-Thaba-Putsoa", is a few kilometres further east, and the first mountain pass, Bushman's Pass, "Lekhalong-la-Baroa", (2266 m) is about 10 km to the west, rising from the village of Nazareth.

Supporting paragraphs: St. Regis River (Montana) Lookout Pass
Answer: Rocky Mountains