Powell would hardly have been able so speedily and successfully to accomplish this feat had it not been for an event which was contemporaneous,—the construction of a transcontinental railway. This enabled him easily to place strong boats and supplies on the banks of Green River. His great voyage, which marks the end of the Wilderness, and the completion of the railway, marking the beginning of an entirely new epoch, occurred the same year. The rivers of the Wilderness were not available for practical transportation. Those east of the Backbone were circuitous and for the most part too shallow for boats of much draft; those west were torrential. Hence the necessity of the Iron Trail. In the search for the best route for such a trail to bind the Hudson to the Golden Gate a great many admirable surveys were made. Every one of the expeditions was profoundly interesting and intimately connected with Wilderness breaking, but it is not practicable here to describe them. The route finally selected was up the Platte, across Green River Valley, to Salt Lake, down the Humboldt, and over the Sierra Nevada to Sacramento and San Francisco. The idea of putting a railway through the Wilderness was early conceived, but owing to numerous obstacles and difficulties as to route to be followed and as to finances, although the numerous surveys were made, nothing definite was done. As far back as 1850 Senator Benton, of Missouri, introduced a bill authorising portions of road to be constructed with gaps where it was supposed a line was not possible. In 1853 Congress appropriated $150,000 for six surveys to be executed by the War Department. The next year $190,000 more were appropriated for three additional surveys. It is thus apparent that Congress appreciated the importance of a line through the Wilderness which should bring the Pacific Coast with its now rapidly developing interests closer to the seat of Government. In the dissension which began to rend the country concerning the slavery question and State rights, there was danger of secession in that direction as well as at the South. The military importance of such a railway was beyond discussion. General Sherman, who knew the conditions thoroughly and had gone in 1846 to California, declared the Government could well afford to build the whole line and would make money by the operation, as it was indispensable for the transportation of troops and supplies. [Illustration: The Thousand Mile Tree. A hemlock 1000 miles from Omaha. Photograph by C. R. Savage.]