Traveling northwest from Omaha you just about can’t get away from Lewis and Clark’s exploration of the area. Trails, overlooks, parks, historical monuments, etc. all dot the landscape, denoting some event along the path of this daring company. Charged with finding a water route to the Pacific and to examine the newly purchased land of Louisiana, the party chose the Missouri River as their guide across the Plains and into the mountains.
That there were mountains along their way was not a surprise to them. Stories from French trappers, Plains Indians, English traders from the west coast all told of a great range of mountains running north and south through the country. What was unknown was whether there was a water route through this range, a gap that could be exploited for trade east and west.
Paddling their boats up the Missouri the men were not surprised to suddenly come upon a point where the river entered the mountains, a cut deep into the living rocks surrounding the stream but not blocking its travel. Happily this was called the Gates of the Mountains and the explorers hoped to push through this area and find a stream on the other side that would take them to the Pacific coast.
Traveling further up river past the Gate they were pleased to see the river continued its journey into the mountain range.
These were the mountains they were expecting to find, except they weren’t. Although they looked like the descriptions of the Rockies they had gotten from several sources, these are simply upthrust ridges pushed up by the actual Rockies arising further west. The river actually runs through this ridge for only about 2-3 miles and then returns to the Plains, crossing a great valley where the current city of Helena, MT sits.
Following the Missouri was eventually a dead end for the Corps. Just north of Triple Forks, MT three rivers come together to form the Missouri, significantly eastward of where the Rockies loom above the Plains as the Bitterroot, Missions, and the ridges found in Glacier National Park.
These mountains are all sedimentary rock, the layers which were formed at the bottom of ancient oceans that covered this area hundreds of millions of years ago. The oldest limestone here is over 1 billion years old. The effects of the pressure on the once-flat sea bottom can be seen in the tilted layers of rock throughout the gap.
Within this area is also a site with more modern impact. Just at the opening of the Gate is Mann Gulch, site of a wildfire in 1949 that claimed the lives of 13 smokejumpers. It was the investigation into these deaths that began modernization of wildfire fighting in this country; most innovations currently in use that improve the fighters’ safety and ability to deal with the unpredictable nature of these fires started with this one.