A very small part of the remainder is used for residential and commercial purposes, the rest being barren mountains, deserts, swamps, and forests.

Of the total in farms a little more than one-half was improved, 478,000,000 acres altogether, a per capita average of 5.2 acres; and a little less than one-half was unimproved, 400,000,000 acres altogether, a per capita average of 4.3 acres.

The improved land produced not merely food but many kinds of materials, such as cotton, wool, hides, and lumber, while much of the unimproved land was either in farm wood-lots, or in rough range pasture.

Of course the kinds and amounts of produce per acre vary with the climate, particularly with sunshine and rainfall; possibly the proportion of the area of the United States that is true desert and infertile mountain land is greater than that of any other equal area in the temperate zones.

The actual productive capacity per acre of the lands of America cannot be expressed in a very helpful way as a general average per acre, but each area must be carefully studied in respect to its climate, rainfall, and possibility of irrigation and drainage.