My dear McClellan,—I have succeeded in securing your detail to take charge of the Western party in the Northern Pacific Railroad survey.
You will get the orders to-day, and be directed probably to repair to New Orleans, and there await instructions. The route is from St. Paul, Minn., to Puget Sound by the great bend of the Missouri River through a pass in the Rocky Mountains near the 49th parallel. A strong party will operate westward from St. Paul; a second but smaller party will go up the Missouri to the Yellowstone, and there make arrangements, reconnoitre the country, etc., and on the junction of the main party they will push through the Blackfoot country, and, reaching the Rocky Mountains, will keep at work there during the summer months. The third party, under your command, will be organized in the Puget Sound region, you and your scientific corps going over the Isthmus, and will operate in the Cascade Range, and meet the party coming from the Rocky Mountains.
As soon as my force is at work in these mountains, I shall push forward with a small reconnoitring force and find you, and, after conference with you, arrange the entire plan of operations.
Your scientific corps will consist of a physician and naturalist, an astronomer, a draughtsman and barometer man, and an officer of the artillery, Johnson K. Duncan, who, I am informed by Foster, is a strong friend of yours, and will work under you. You will have authority to call upon the officers and troops stationed in the Territories of Oregon and Washington, and I have no doubt you will be able to secure valuable assistance. At the same time funds will be placed in your hands to hire suitable guides, hunters, etc. A complete set of instruments and appliances will be sent with the necessary instructions.
Your friend, Professor Baird, is arranging the natural history part of the business. The expedition will be altogether the most complete that has ever set out in this country, and if we are true to it, the results will be satisfactory to the country. The amount of work in the Cascade Range and eastward, say to the probable junction of the parties at the great bend of the north fork of the Columbia River, will be immense. Recollect, the main object is a railroad survey from the headwaters of the Mississippi River to Puget Sound.
We must rely upon the ordinary astronomical observations in the field, upon the odometer and barometer and the compass, for getting the direction, length, and profiles of routes. With the sextant for determining height along the route, and with a good sketcher and draughtsman, you will be able to get good results. I may get for you a small detachment of sappers, and I shall try to get you assigned to duty according to your brevet rank.
I telegraphed you some days since, asking your views, but in consequence of your great distance from Washington it was essential to act at once. Knowing your views so intimately in relation to such service, and venturing on our long acquaintance and mutual friendship, I have in the strongest terms pressed your case, on the ground that, could you be consulted, the duty would be sought by you. In my telegraphic message I informed you that I was put in charge of the duty in consequence of my civil position. It has been done at the joint desire of the War Department, of the Department of State, and of the Department of the Interior. Officers have volunteered for the service, and I shall receive the services of several very valuable and experienced men. I have in the strongest terms taken the ground that my having left the army and standing in a civil position would not, under the circumstances of the case, be any objection on your part to acting under my direction.
As your friend, and knowing the opportunity for distinction it would give you, I would not hesitate for a moment.
One word more as to the railroad survey. We must not be frightened with long tunnels or enormous snows, but set ourselves to work to overcome them. When you reach New Orleans you will find your instructions.
Truly your friend,
Isaac I. Stevens.