The importance of these concentration points is further demonstrated by a classification by States of the spring and winter wheat production which appears in the following table:

TABLE 15.-Average annual production of spring and winter wheat by principal producing States for the calendar years 1913 to 1917.1

1 Compiled from Yearbooks of Department of Agriculture, each year's figures taken from the year of issue. The Yearbooks do not give corrected figures.

The table shows that the production of winter wheat extends through a broad belt including Nebraska on the north and extending into Texas in the southwest. The most productive area centers in Kansas reaching north into Nebraska, south into Oklahoma, and eastward through Missouri, Illinois, Indiana, and Ohio. Wheat is not grown successfully in the southeast where the warm, humid spring weather permits fungous diseases to injure the crop, and where the mild winters frequently give the plant a premature start only to be damaged or destroyed by late frosts.1

Spring wheat, on the other hand, is highly localized in the Northwest, from Minnesota to Washington, with North Dakota the leading producer. The Rocky Mountain plateau cuts athwart this region

1 Finch and Baker, Geography of World's Agriculture (1917), pp. 14, 15, 18.

so that the Washington area (the Palouse and Big Bend districts) must be considered a secondary zone of production.

It is apparent, then, that Duluth and Minneapolis are in position to command the shipments of spring wheat while Kansas City, Chicago, and St. Louis have ready access to the winter-wheat areas. Omaha and Milwaukee are in position to derive a certain proportion from each crop. Kansas City is undoubtedly the leading winter wheat market, although the exchange publishes no figures distinDiagram A.

WHEAT PRODUCTION (BU. PER SQ. MI.] IN THE

PRINCIPAL GRAIN STATES

guishing between the two varieties. The effect of the localization of spring wheat appears in the following table, which shows the distribution of spring and winter wheat shipments between Minneapolis, Duluth, Chicago, and St. Louis for the five-year period 1913 to 1917 (no data being available for Kansas City or Omaha):

TABLE 16.-Distribution of spring and winter wheat shipments at specified markets 1913 to 1917.1

! No statistics available for Kansas City or Omaha. Receipts at Kansas City are practically all winter wheat.

PRIMARY MARKETS AND CORN PRODUCTION.-The United States corn crop is the largest cereal crop produced in any country. While production extends generally throughout the United States, the great bulk of the crop is consumed on the farm in feeding so that shipments are made largely from the fields of greatest production. Diagram B.

CORN PRODUCTION (BUSHELS PER SQ.MI.) IN THE

PRINCIPAL GRAIN STATES

Diagram B shows that the area of heaviest production extends from the Mississippi Basin in western Iowa and eastern Nebraska across Illinois and Indiana and into Ohio.3

As both the table and Diagram B indicate, the markets in or near the States of Iowa, Illinois, Nebraska, Indiana, Missouri, and Ohio are most accessible to surplus corn production. The rank of these corn markets has been shown at page 20.

The following table gives the classification by States of the average annual production of corn for the period 1913-1917:

3 The temperature requirements of different varieties of corn vary widely. Some southern varieties need an average frostless season of 180 days and mean summer temperature of 80°. Practically no corn is grown where the mean summer temperature is less than 66°, or where the average night temperature during the three summer months falls below 55°. Consequently the production of corn along the northern border of the United States and at the higher elevations in the West is negligible. (Finch and Baker, p. 29.)

TABLE 17.-Average annual production of corn in the principal producing States,

1913 to 1917.1

Compiled from Yearbooks of the Department of Agriculture, 1914 to 1917, each year's figures being taken from the Yearbook of the following year to obtain corrected figures, except 1917, which is from the 1917 Yearbook.

PRIMARY MARKETS AND OATS PRODUCTION.-Oats, like corn, is grown chiefly for feeding purposes. The geographical distribution of the oats crop, as Diagram C shows, is similar in a general way to Diagram C.

OATS PRODUCTION (BUSHELS PER SQ. MI.) IN THE
PRINCIPAL GRAIN STATES

that of corn, except that the former cereal is grown much more extensively in the Northwest.

The more northwesterly trend of the oats belt and the relatively heavy production in Minnesota and the Dakotas enables Minneapolis and Milwaukee to obtain a volume of receipts which places them in second and third rank, respectively, as oats markets. (See Table 4. p. 21.) Oats also follows corn production in the Central West because of its use in crop rotation with the latter cereal.'

The figures of average oats production, by States for the period 1913 to 1917, are shown in the following table:

TABLE 18.--Average annual production of oats in the principal producing States, 1913

Compiled from Yearbooks of the Department of Agriculture, 1914 to 1917; each year from the Yearbook of the following year to obtain corrected figures, except 1917, which is from the Yearbook of the same year..

From the table it appears that Iowa and Illinois, the leading corn States, are also first in the production of oats. These States are directly tributary to Chicago and Milwaukee, the first and third markets in oats receipts. Minneapolis, the second largest oats primary market, is tribuary to the Dakotas, Iowa, and the Minnesota oats belt.

PRIMARY MARKETS AND BARLEY PRODUCTION.-Diagram D (following) shows the trend of barley production into the Northwest.

4 See Finch and Baker, Geography of the World's Agriculture, p. 35. In the great oats-producing region of the central United States this crop is particularly important not only because the grain is desired for feeding work animals, but alsɔ because it offers a spring grain needed in the crop rotation with corn, spring wheat not being adapted to this region. As oats are sown in the spring, before corn-planting time, the crop does not require the early removal of the corn, as is the case with fall-sown wheat, and as oats do not mature until after the corn is laid by in early July, there is very little competition with this more profitable crop for labor at critical times of the year.

5 Most of the barley in the United States is grown in Minnesota and the Dakotas; California also raisesa large amount, eastern Washington and the famous barley district of eastern Wisconsin constituting the other important centers. A considerable acreage of barley is also found in Kansas, Iowa, eastern Michigan, and central New York. The barley used for brewing is grown almost entirely to the west and northwest of the Great Lakes. Barley is not grown to any extent as yet in the South. (Finch and Baker, p. 40.)