During the building of the dam the valley below was the scene of unprecedented activity. A million-dollar diversion dam was constructed across the Salt River to divert the stored water into thousands of miles of canals; power plants, pumping plants, transmission lines, and a thousand and one engineering details were completed in advance of the great day when the turbulent floods of Salt River would be conserved and led to the thirsty lands. On March 18, 1911, former President Roosevelt, in the presence of an assemblage of nearly 1,000 people, formally dedicated the structure which fittingly bears his name. By the simple pressure of an electric button the enormous gates weighing 60,000 pounds were raised and released the pent-up floods for irrigating nearly 200,000 acres of Salt River Valley. The swift passing of years has been marked by marvelous progress in this desert valley. In 1902, when the work was started, the assessed valuation of the country, of which the valley is the larger part, was $5,000,000. In 1916, the taxable property values were $72,000,000. In 1913, the first crop census of the project was taken and showed an irrigated acreage of 159,170, and a gross value of crops of $4,775,000. In 1917, the total acreage watered was 201,600; the gross value of crops was $13,692,000. During the same period the number of farms increased from 3,600 to 4,326. The net cost of the entire project to June 30, 1917, including $3,500,000 for the Roosevelt Dam, was $11,367,000. The annual returns from the land irrigated by it are more than $3,000,000 in excess of this amount. The gross value of crops in 1917 was almost equal to that of New Hampshire and Rhode Island in the census year of 1909. In October of 1917 the Roosevelt Dam, canal system, and power plants were formally transferred to the Water Users’ Association, under whose management the project henceforth will be operated. WRITTEN ESPECIALLY FOR THE MENTOR BY C. J. BLANCHARD ILLUSTRATION FOR THE MENTOR, VOL. 6, No. 17, SERIAL No. 165 COPYRIGHT, 1918, BY THE MENTOR ASSOCIATION, INC. [Illustration: ARROWROCK DAM, IDAHO--THE HIGHEST DAM IN THE WORLD] _RECLAIMING THE DESERT_ _The Highest Dam in the World_ FIVE