84 
EL SANGRE DE CRISTO PASS AND SAN LUIS VALLEY. 
it is 68 miles from this point to our camp of July 16lh, above Fort Atkinson ; and the ascent 418 
feet, or six feet two inches to the mile. But if the river be followed between these points, the 
distance will be increased and the ascent correspondingly diminished; or, by taking a more direct 
course, the distance would be lessened, slightly increasing the grade, which will be best seen by 
a reference to the section of this part of our route. For eighty-nine miles west from this camp, 
following the banks of the river, we ascended five feet four inches to the mile; and in the 
succeeding 105 miles, to a short distance below Bent’s Fort, the average ascent per mile was 
seven and three-fourths feet; and twenty feet seven inches per mile for the next thirty-four miles 
to the mouth of the Apishpa. The general section which accompanies this report, from this 
point to the Huerfano butte, is that of the line followed by our wagons, and the distance, eighty 
miles, given on it, exceeds by one-fourth the length of the line necessary for the construction of a 
railroad between these points. The general ascent to be gained by the shorter line, is twenty- 
eight feet ten inches to the mile. The natural grade for fourteen and a half miles above this 
point, following the river, is fifty-two feet ten inches per mile, which brings us slightly*within 
the eastern spurs of the Rocky mountains. 
The summit (so to speak) of the great interior trunk of the continent, upon which nearly all its 
mountain ranges, masses, and peaks are elevated, is reached, upon this line, at the Huerfano 
butte, which is 6,099 feet above the sea, and 5,109 feet (nearly a mile) above our camp near 
Westport; and the whole of this remarkable ascent—which has its counterpart, more or less 
approaching the same elevation, by whatever line the mountains are approached from the east— 
is gained by the easy grades given, over a continuous plain, without once passing a remarkable 
hill or making at any point a considerable descent. 
The estimated distance from our camp, of August 9th, on the Huerfano river, by the circuit 
indicated for a railroad, ascending the stream through the large amphitheatre drained by the river 
and its branches, to the Black butte, (twelve miles,) to Williams’ Pass fork, (two miles,) and 
Gunnison’s creek, (three miles,) and thence ascending the latter stream to the summit of El 
Sangre de Cristo Pass, is from twenty-four to twenty-six miles, and the difference of elevation 
2,354 feet—an average of ninety-eight feet and one inch to the mile for the shorter, and ninety 
feet six inches for the longer distance. The altitude of the summit of this pass is 9,219 feet above 
the sea; and of the highest point passed by our wagons, 9,358 feet; the altitude of the lowest 
and nearest peak to the pass being 9,852 feet. Captain Gunnison says, “ a single grade can 
easily be carried from the summit of this pass to the gorge of the Huerfano river, (just below our 
camp of August 9th), but two—one along Gunnison’s creek, and one on the river—would proba¬ 
bly be preferable.” The Sangre de Cristo creek rises near the summit of the pass, and descends 
in a general southwestern direction, through a narrow ravine, for 7.09 miles, which thence 
gradually opens for six miles towards the valley of San Luis. The mountains on either side 
rise several hundred feet above the stream. The descent of the stream from the summit of the 
pass, is 101 feet per mile for the first mile and three-fourths, and 103 feet per mile for the suc¬ 
ceeding mile and thirty-four hundredths. Six miles below this point we left the creek, and 
rose to a plain extending along the base of the mountain spurs, which we followed for 4.57 miles, 
to Utah creek, near Fort Massachusetts, having descended twelve feet to the mile for the entire 
distance, 10.57 miles. By descending from the summit of the pass along the side of the mountain 
on the right of the creek, a road can be constructed, throwing a larger proportion of the descent 
upon the lower part, where it should be carried on a mass of low hills to the plain indicated 
above, which subsides gently into the valley of the Rio Grande del Norte. 
The broad open valley of ,San Luis, enclosed on the east by the mountains just crossed, and 
on the west by the chain of the Sierra San Juan, and drained by the Rio Grande del Norte and 
its tributaries, is so level that a railroad can be carried over it in any desired direction. From 
Utah creek we descended 49 feet per mile for 10.93 miles, to White Mountain spring; and 
14 feet per mile for the following 13.46 miles, to near Roubideau’s Pass. This pass was 
