average of 1,389 acres per farm, had larger farms than any upper basin State except Wyoming. Livestock raising was the major farming activity on large farms. Between 1930 and 1940 the number of large farms (those over 100 acres) in the lower basin increased 2.1 times, while the percent of the total area of such farms increased only 1.6 times. The most significant increase in large farms took place between 1935 and 1940. During that period the number of farms of fewer than 10 acres was cut almost in half.

The general trend is toward larger farms. The increase in the size of ranches is due partly to the decrease in the number of livestock the public range can support. Crop farms are increasing in size and number in certain areas because improved machinery makes possible higher efficiency in farm operation.

Irrigated farm acreage. The average number of irrigated acres per farm in the lower basin decreased slightly during the period 1910 to 1940. The decrease was due largely to the increase in number of irrigated farms, with a lesser corresponding increase in irrigated acreage. The Little Colorado division had the smallest irrigated farm units as well as the greatest decrease in irrigated acreage per farm. The number of irrigated farms in that division increased from 554 in 1910 to 1,942 in 1940, but the total irrigated acreage increased only 35 percent. The small size of these units results from the high percentage of Indian farms and the large number of subsistence white farms.

Farm operation. Full renters or tenants made up 14 percent of all farm operators and farmed about 19 percent of the cultivated land in 1940. Owner-renters or

part owners (those renting a portion of the farm lands they harvest), operated only one-tenth of all farms, but farmed more than one-third of all the crop land harvested in 1940. Owner-operators made up the rest of the farmers and represent the largest group, harvesting nearly 50 percent of the crop land in 1940 (fig. 10).

While the extent of farm leasing in the lower basin is below the national average, it presents a problem in certain irrigated sections of the basin, mainly because the terms of the individual leases fail to make provision for

preserving the productivity of the soil and for the upkeep of improvements on the farms. Land that has been in alfalfa for a number of years, however, is often leased to vegetable growers for a period of 1 to 3 years, the plan being to replant to a soil-building crop after the lease has expired.

Value of farm lands and buildings.-Land values vary widely depending upon location, soil quality, topography, water supply and other factors. Raw land, without prospective irrigation possibilities usually sells for $1 to $10 an acre. Irrigated land sells for $100 to $250 an acre with the higher prices more common in the Boulder and Gila divisions.

The decrease in the total value of all farm land and farm buildings from 1930 to 1940 was 24.2 percent, as compared with 29.7 percent for the entire country. The average value per farm of all land and buildings in the basin is 50 percent above the average for the United States, while in the Gila and Boulder divisions, the average farm value is twice that of the entire country.

The decrease in the per-acre land values during the 1930 to 1940 period is attributed to a number of factors. Agricultural prices declined during this period which was one of the major economic depressions. Considerable land of much lower value than that previously farmed was purchased. The acreage of farm land doubled during this period, whereas the total number of farms increased from 21,193 to 25,795, an increase of only 17 percent; consequently the value per acre of farm improvements was not in proportion to the increase in acreage.

Land values have risen since the 1940 census was taken, and in many sections of the lower basin a land boom is under way. Lands in financial distress 10 years ago now are selling generally at double and treble the prices of 1933 to 1935.

Farm products and value.-The basin is favored by a climate ideal for producing winter crops. Citrus fruits and winter vegetables returned $3,800,000 and $7,300,000 respectively to the farmers of the basin in 1939. Dur

ing the months of December and January the country is largely dependent for its supply of lettuce on Arizona and the Imperial Valley of southern California. In 1943 the Salt River and Yuma Valleys in Arizona shipped 6,600 carloads of winter lettuce, shipments being consigned to 45 of the 48 States. In 1939 the per capita value of farm products of the basin was $97, as compared with $75 in the Nation.

Livestock and livestock products sold in 1939 made up 36.7 percent of all agricultural production in the basin, as compared with 35.5 percent for the entire Nation. Feeder cattle, sheep, and goats are the predominating livestock. Only a few hogs are raised in the area. An increase in production of feed crops may result in a considerable increase in the proportionate value of livestock and livestock products.

The sale of dairy products is important in some irrigated areas. Dairying probably will increase, but it is doubt

MINERALS AND MINING

The first white settlers in the lower basin were adventurers, many of whom originally had set out to seek gold in California. It was natural that they should prospect the region through which they traveled. Significant gold and silver strikes were made in the 1880's. These strikes led to booms with their attendant influx of people. But the mining industry, as developed in the last century, was a precarious business. There was no orderly development, no scientific method of locating ore deposits, or any attempt at establishing this major resource as the basis of a stable industry. Numerous ghost towns throughout the entire area give mute testimony to the feverish and impetuous exploitation of the ore resources.

Today, mining and mineral resources are of vital importance to the region, but attitudes and methods have changed. Emphasis is now upon sound planning and development with full utilization of modern scientific knowledge and methods.

Valuable minerals are well distributed, and important mining operations are found in many parts of the lower basin. (See appendix, maps entitled "Mineral Resources, Colorado River Basin.") Mining camps are markets for farm crops, and mines consume large quantities of the lumber produced by local lumber mills. The transportation of ore, metals, and mining supplies is one of the main sources of revenue for railroads and trucking companies. Mining properties furnish one of the principal tax sources for State and local governments. Mining enterprises provide employment for many of the residents and have made possible the development and improvement of many isolated and remote areas.

Of all minerals mined in the lower basin, copper is most important. Each year, since 1910, Arizona has ranked first among the States in copper production, and probably will continue to hold such rank for many years. Large mines are operated at Bisbee, Morenci, Superior, Globe, Miami, Ray, Ajo, and Jerome, Ariz. The remaining

copper deposits have been estimated to contain about 23 billion pounds which could be recovered at costs ranging from 6 to 18 cents per pound. The largest reserve of ore in the basin is found at Morenci, Ariz., where proven future supplies total 300 million tons of ore containing from 20 to 25 pounds of copper per ton. (See figs. 11 and 12.) Gold ranks second in annual gross income from mining in the lower basin. About 50 percent of the gold produced is recovered as a byproduct of copper ores. The largest known reserves of gold are found in ores primarily valuable for their base metals. Mines in high-grade ore districts have been sporadic in production, their output fluctuating with prevailing market conditions. The Delmar, Nev., district, the largest of the straight gold-andsilver-producing areas, produced in 1940 minerals valued at $130,700. Little commercial grade ore remains in any of the known gold-ore deposits.

Silver is third in importance as a source of income from mining. About 75 percent of the silver produced comes from copper ores, and a large part of the remainder is produced as a byproduct of the lead and zinc mining industry.

Zinc production is handicapped by the distance to zinc smelters. High shipping costs make the development of low-grade ore deposits difficult and sometimes impossible. Zinc deposits are generally associated with lead or copper. The largest zinc ore reserves are in copper deposits but these are low-grade, and mining and milling costs are high. From the standpoint of production costs, the most important zinc reserves are those associated with lead. One of the largest of these is found in Mojave County near Boulder Dam. The construction of an electrolytic treatment plant in this district, using low-cost power developed at Boulder Dam, would greatly stimulate zinc production. Considerable amounts of zinc ore are produced in the Superior, Patagonia, Nogales, Bisbee, Iron King, Mammoth, Hillside, and San Xavier districts of Arizona, and the San Simon and Lordsburg districts of New Mexico.