Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 1, Pt. 2

ROCKY MOUNTAIN PASSES.
difficulty, and involve a considerable detour as regards the approach from the north of the Missouri.
The northern Little Blackfoot Pass is the one by which Mr. Tinkham crossed the Rocky mountains the third time, and in November; is at the source of one of the north forks of Hell Gate river,
termed by Lieutenant Mullan Little Blackfoot river, and is remarkably easy. The Indian trail
passing here is a well-worn road, and is perfectly practicable for wagons. The dividing ridge is
an inconsiderable hill, three hundred to five hundred feet high. Between this pass and the prairies
of Marias, Teton, and Sun rivers, the country is somewhat irregular and broken. The barometer
gave the summit elevation of the pass at 6,250 feet above the sea, which will probably, in a
discussion of the observations, be reduced to less than 6,000 feet.
In pursuing this route, Mr. Tinkham kept south of the Missouri until the gate of the mountain
was turned; and for information of the approach north of the Missouri, I am indebted to an
exploration under Lieutenant Mullan. In a trip to Fort Benton and back to the St. Mary's
valley in March, Lieutenant Mullan brought a wagon through this pass, making the journey from
Fort Benton to Cantonment Stevens, a distance of two hundred and ninety-six miles, in twelve
travelling days; and there seems scarcely a doubt as to there being an excellent railroad approach
to it north of the Missouri, on the route pursued by him. He kept on the high table-land between
the Missouri and the Teton, crossed the Sun and the Dearborn rivers a little south of the crossing
of the main party in September last; then keeping farther to the south, he crossed the small
Prickly Pear creek, and crossing a divide, the one taken by Mr. Tinkham in November, he
found the inclination so gradual, that he descended from it not only without locking wheels, but
on a run. His course then was by the Little Blackfoot and Hell Gate rivers. A little work is
required on this route in cutting timber to get an excellent wagon road. The eastern approach
is estimated as practicable with a grade of fifty to sixty feet per mile, the passage of the ridge
with a two-mile tunnel, and the western descent with a grade of thirty feet. The valleys of the
Little Blackfoot and Hell Gate rivers, from the pass to the junction with the Blackfoot river, are
more open and regular than the valley of the latter. Its descent is regular, and, by the barometric
observations, is, from the foot of the summit divide to Hell Gate, ninety-five miles, twenty-two
and a half feet per mile. The route for the greater portion of the way keeps on the bottom-lands,
which are generally unobstructed by tiniber, sufficient wood always lining the streams for use as
fuel, whether for camping or settlement. For lumber, the woods of pines and other evergreens
are sufficiently near fbr use; but the thick woods do not crowd the valley as in some places
on Blackfoot river. An open growth of yellow pine occupies the bottom-lands for a few miles
in the lower part of the valley, and the cotton-wood growth sometimes stretches across the bottom.
The construction of a railway down this valley will probably make necessary the bridging or
turning of the main stream several times. Curves will be easy, and the grades used not generally exceed the natural descent of the valley.
The route is indicated on the sketch in dotted lines. It will increase the route forty-four
miles, but it may give the means, at the eastern extremity of the Little Blackfoot valley, to
make a junction with a road from Council Bluffs. This connexion is indicated on the map. The
mountains shutting down on the Missouri, on both banks, to the gate of the mountains, may present an earlier junction of the two routes. The thorough examination of this route, and of the
Little Blackfoot trails, writh which it connects almost immediately west of the divide, and of
the Hell Gate Pass, all three of which have been examined by Lieutenant Mullan, and the full
description of which will be found in his reports herewith submitted, will become important should
a good connexion be found through the Black Hi]ls with the roads moving westward through
Iowa and Missouri; or, should it be found practicable, through the same hills to make a straighter
route from the Bois des Sioux than that north of the Missouri.
The southern of the Little Blackfoot routes is singularly direct, and, in common with the iell
Gate route and northern Little Blackfoot, requires little or no labor to make it practicable- for
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