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

 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. The Lewis and Clark National Historic Trail is a route across the United States commemorating the Lewis and Clark Expedition of 1804 to 1806. <SEP> 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. <SEP> 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.  Lewis and Clark Pass is the only roadless pass on the entire Lewis and Clark National Historic Trail.  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.  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. <SEP> 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.