...until I found Fifteen Thousand Miles by Stage by Carrie Adell Strahorn (and digitized by Google). One of the chapters in Strahorn's book tells of a stagecoach trip from Helena to Missoula that took place in the late 1870s. I have excerpted the part that talks about the Deer Lodge to Missoula leg (through the Hellgate Valley):
From Deer Lodge to Missoula we forded the Deer Lodge River seven times and crossed it twice on bridges. It was a veritable Lovers' Lane leading through bowers of wild roses; oftentimes the rose bushes arched over the stage road and joined their blooms in a wealth of beauty and untrammelled luxuriance, filling the air with their fragrance and our hearts with admiration and joy. It was an expanse of earth set apart for wild growth, not only of flowers but of wild berries and wild animals.It paints a pretty picture, doesn't it? I think you'll agree that finding this description of the Hellgate Valley in the late 1870s is the next best thing to finding a description from my ancestors themselves.
From the seat with the driver there were views of long avenues ahead and most too often the glinting water in the distance betokened another fording of the river. Though clear as crystal it was deep and swift and when the leaders of our four-horse team reluctantly made the leap down the bank it always sent creepers up my spine. The water grew deeper at every crossing from the many lateral feeders of canyon springs, and my breath stopped and choked just a little higher in the throat as I leaned forward with contracted muscles as if it helped the horses drag the burden over the rocky river bed.
Grand old pine trees, tall and stately, were gathered in forests on either side, with the ground beneath free of underbrush except for the rose and berry bushes in the more sunny openings near the streams. It was like one grand, continuous park, with the half dead pines covered with an inch of green moss, hiding all marks of death's decay.
A dark moving object ahead of us in the open roadway suddenly appeared in full view and the jehu pulled in the reins to get a steady look ahead. Then he exclaimed with a strong oath "that that damn thing ahead of us is a bear." He called to the passengers to get their shooting irons ready for there might be trouble ahead. Those inside thought of the dreaded Indian, and were greatly relieved to know it was only a bear that caused the call to arms. The horses reared and plunged from instinctive fear and we gained only a little on the king of the American wilds.
The driver lashed the poor brutes into a chase until there was grave fear that they would wheel suddenly backward and cause a serious accident. But the bear reached the river first, and by the time the stage reached the ford old Bruin was lifting his head out of the water away down on the opposite bank, where he emerged and shook his shaggy coat and scrambled into the brush.
It was the only spirited event of the trip, and early in the afternoon we were in the great Montana garden of the Hell Gate River. It seemed a curious name to give to such a beautiful stream, but it comes from the black and intricate passage through the rocky pass of the same name near Missoula.
Missoula was not of enough importance to have a place on the map, but it was a productive section that has since made itself known to the world. Peaches, pears, and melons--my how good they were after a long famine of such luxuries!
For your reference, I am including a snippet of a Rand McNally map from 1879. I have highlighted the described route in yellow, and marked the approximate location of present-day Clinton with a red "X." Please note that the Northern Pacific RR had not made it to the Hellgate Valley by 1879. Many maps included proposed/expected routes of the various railroads before they were actually constructed. When it was constructed, the NPRR largely followed the Mullan Road.