26 DRY-FARMING 
nation of this map proves that nearly one half of the 
whole area of the United States receives 20 inches or 
less rainfall annually; and that when the strip re- 
ceiving between 20 and 30 inches is added, the whole 
area directly subject to reclamation by irrigation or 
dry-farming is considerably more than one half 
(63 per cent) of the whole area of the United States. 
Eighteen states are included in this area of low 
rainfall. The areas of these, as given by the Census 
of 1900, grouped according to the annual precipita- 
tion received, are shown below: — 
Arp To SEemri- Totat ArEA LAND 
“ARID GROUP Surrace (Sq. Mixes) 
Arizona. www 112,920 
California. . . .. . 156,172 
Colorado . ..... 103,645 
Idaho ....... 84,290 
Nevada. ...... 109,740 
Wtabe ao: @ se ws 82,190 
Wyoming ...... 97,575 
Total s « # « « 746,532 
Semiarip To Sus-HuMID GRoupP 
Montana . ..... 145,310 
Nebraska . . .... 76,840 
New Mexico . . .. . 112,460 
North Dakota ... . 70,195 
Oregon. . . ... . 94,560 
South Dakota ... . 76,850 
Washington . ... . 66,880 
Total « « « « # « 653,095 
