The same general boundaries that divide the State topographically also designate the three agricultural belts. The Red River Valley and Drift Prairie are combined in what is known as the black-earth belt, the Coteau du Missouri constitutes the farming-grazing belt, and the Missouri Slope is the grazing-forage belt. In the black-earth belt the farms are usually small, averaging less than 400 acres in extent. Here the average annual rainfall varies from 18 to 24 inches, 6 to 8 inches of which falls during the months of May and June, when it is most valuable to small grains. The black-earth region was the first part of North Dakota to be settled. Furs were the object of the earliest white settlers there, but the value of agricultural pursuits was by no means overlooked even during that early period. Alexander Henry, Jr., the fur trader who foresaw that the Red River Valley would be good agricultural land if the transportation problem could be solved, tells in his diary of planting a garden as early as 1800 at his trading post at the mouth of the Pembina River, where he raised carrots, cabbages, beets, potatoes, and other vegetables. Nor was he free from the evils which beset the modern farmer: his crop was highly satisfactory for several years, but in 1808 everything was eaten by the grasshoppers which swarmed across the land. Henry's agrarian ventures were secondary to his fur trading, however, and it was not until the friends of Charles Cavileer settled at Pembina in 1851 that a permanent agricultural colony was established in the State. An earlier settlement by the Selkirkers of Canada in 1812 had been short-lived. When the Cavileer colony arrived, however, the Selkirk colonists, now established at Fort Douglas, Winnipeg, not only provided Cavileer himself with a bride but also supplied his people with seed wheat, oats, barley, and field peas--an invaluable contribution. For almost 20 years the little settlement at Pembina was the only farming community in the State. Dakota Territory had been opened to settlement January 1, 1863, and free lands were offered to anyone over 21 years of age who would cultivate and improve his 160-acre homestead, and live on it 5 years. If he wished, he could also obtain a tree claim of 160 acres.