Question: What is the only roadless pass on the Lewis and Clark National Historic Trail?

Context paragraphs:
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.

Rex Ziak: Rex Ziak (pronounced "zeek") is a writer, historian, tour guide, and documentarian, who lives in Naselle, Washington, United States.  Known for his Lewis and Clark studies, he is the author of "In Full View."  After careful study of the expedition's journals and of the geography of the Columbia River estuary, Ziak discovered the previously unknown fact that from November 7, 1805 to December 6, the Lewis and Clark expedition stayed in what is now Pacific County, along the Long Beach Peninsula.  This finding took six years for Ziak to piece together, using the comments in the expedition's journals to find the locations the explorers stopped at on their trip.  A controversy arose between Oregon, long considered the end of the expedition, and Washington's historians over Ziak's findings, with many historians in Washington and elsewhere supporting his discovery and many in Oregon opposing it.  In 1999, soon after his announcement, Ziak and David Nicandri, director of the Washington State Historical Society, began petitioning to give the newly found ending location, a camping spot called Station Camp, National Landmark Status.  In addition, that year, US Representative Brian Baird had an amendment passed that changed the "federal designation of the Lewis and CLark National Historic Trail as ending not in Oregon but in Oregon and Washington."

Arrow Rock, Missouri: Arrow Rock is a village in Saline County, Missouri, United States, located near the Missouri River.  The village has important historical significance related to westward expansion, the Santa Fe Trail and 19th century artist George Caleb Bingham.  The state’s first state historic site is located here and the entire village is part of the National Historic Landmark Arrow Rock Historic District, designated by the Department of the Interior, National Park Service in 1963.  Many structures within the village are also individually listed on the National Register of Historic Places.  Several locations are also certified sites of the Lewis and Clark National Historic Trail and the Santa Fe National Historic Trail.

Kings Hill Pass: Kings Hill Pass is part of the Kings Hill Scenic Byway which passes through the Little Belt Mountains in the Lewis and Clark National Forest in Montana, United States.  The route is home to a wide variety of wildlife and provides many recreational opportunities for travelers on the route.  The Byway is a 71-mile route that begins on US Highway 89 at its junction with US Highway 12.  From the junction the Byway travels north through the Lewis and Clark National Forest through the communities of Neihart and Monarch Montana and on to its junction with US Highway 87.  The route offers access to the Showdown Ski Area and Sluice Boxes State Park.  The route travels over the Kings Hill Pass near Monarch Montana which snow removal crews work to keep open throughout the winter season.  Kings Hill Pass is at an elevation of 7,393 feet.  There is an observation tower that offers views of the Lewis and Clark National Forest that is popular with visitors.

Sleeping Giant Wilderness Study Area: Sleeping Giant Wilderness Study Area is a non-motorized recreation area located on the west side of the Missouri River and Holter Lake located about 30 mi north of Helena, Montana.  Designated as a wilderness study area in 1981, the Sleeping Giant Wilderness Study Area contains approximately 6666 acre of nearly roadless land, about half of which is forested.  A portion of the Lewis and Clark National Historic Trail is contained inside the study area.

Lewis and Clark National Historic Trail: The Lewis and Clark National Historic Trail is a route across the United States commemorating the Lewis and Clark Expedition of 1804 to 1806.  It is part of the National Trails System of the United States.  It extends for some 3700 mi from Wood River, Illinois, to the mouth of the Columbia River in Oregon.

Traveler's Rest (Lolo, Montana): Traveler's Rest was a stopping point of the Lewis and Clark Expedition, located about one mile south of Lolo, Montana.  The expedition stopped from September 9 to September 11, 1805, before crossing the Bitterroot Mountains, and again on the return trip from June 30 to July 3, 1806.  Traveler's Rest is at the eastern end of the Lolo Trail.  It was declared a National Historic Landmark in 1960 and added to the National Register of Historic Places in 1966.  The boundaries were subsequently revised, and mostly lie within the 51 acre Traveler's Rest State Park, which is operated by the Montana Fish, Wildlife & Parks.  Significant archeological findings made in 2002, including latrine sites with traces of mercury and fire hearths, make this the only site on the Lewis and Clark National Historic Trail that has yielded physical proof of the explorers' presence.  Records made by Lewis and Clark often spell "Traveler's" as "Traveller's".  This spot is largely unchanged from the days of Lewis and Clark.  From this location, Lewis and Clark split up to explore Montana during their return trip, not reuniting until they reached Sanish, North Dakota.

Black Sandy State Park: Black Sandy State Park, located 15 mi north of Helena, Montana, in Lewis and Clark County, is a Montana state park on the shores of Hauser Lake, which is formed by Hauser Dam.  The dam, at an elevation of 3835 ft , was built in the early 1900s and named after former governor Samuel Thomas Hauser.  The park is along the Lewis and Clark National Historic Trail.  The Lewis and Clark Expedition passed through the area in 1805.  Prior to 1980, Montana Power Company owned the land and operated the park as a recreation area.  In 1980, Montana Power turned over management of the park to Montana Department of Fish, Wildlife and Parks (FWP).  In 1982, it was designated a state recreation area.  Later on the land was also turned over to FWP.

Ala Kahakai National Historic Trail: Ala Kahakai National Historic Trail is a 175 mi long trail located on the island of Hawaii.  It is not yet a continuous "trail", but can be accessed at several broken segments along the coastline of the Big Island.  The trail was established to access the traditional Ancient Hawaiian culture along with the natural geology of the island.  The trail was established 14 November 2000 as a National Historic Trail which is managed under the National Park Service.

Lewis and Clark State Historic Site: The Lewis and Clark State Historic Site opened in 2002 and is owned and operated by the Illinois Historic Preservation Agency.  The site, located in Hartford, Illinois, commemorates Camp River Dubois, the camp of the Lewis and Clark Expedition from December 1803 to May 1804.  The site is National Trail Site #1 on the Lewis and Clark National Historic Trail and is located directly off the Confluence Bike Trail, part of the Confluence Greenway.  The site is at the southern end of the Meeting of the Great Rivers Scenic Route.

Supporting paragraphs: Lewis and Clark Pass (Montana) Lewis and Clark National Historic Trail
Answer: Lewis and Clark Pass