The census of 1890 credited Castro County with only nine inhabitants, but settlers came in in sufficient numbers during the following months to justify the organization of a county government on December 23, 1891. By 1900, after a partial exodus of the original population owing to the stringency of the preceding decade, there were 400 inhabitants; since then progress has been on a more substantial basis, and by 1910 the population of the county was 1,850. Early in the present century a considerable colony of German people began settling in Castro County, chiefly in the eastern portions around the little Village of Nazareth. The county seat is Dimmitt, and the only railway station is in the extreme northwest corner at Summerfield. The branch of the Pecos & Northern Texas from Amarillo to the New Mexico boundary was built during the year 1898, and furnishes Castro County with its most convenient shipping facilities.

Ten years ago practically a fourth of the entire county was included within the great ranches operated under corporation or syndicate control, while the rest of the land was parceled into smaller ranch holdings. A number of the conspicuous Panhandle cattlemen have at various times operated in Castro County, and most of the farming has been conducted as an adjunct to the live stock industry, consisting chiefly in the raising of forage crops. The rolling surface of the county contains many dry lakes, and an abundant supply of underground water is found at convenient depth. The possibilities of irrigation are realized, but little development work has been undertaken.

In 1910 there were 327 farms as compared with 76 at the preceding census. The total area of the county is 573,440 acres, of which 289,168 acres were included in farms in 1910, with about 71,000 acres as "improved land," against about 12,000 acres so classified in 1900. The live stock in 1910 comprised 8,211 cattle; about 3,200 horses and mules; 21,358 hogs; and 3,406 sheep. In hay and forage crops, 21,027 acres were planted in 1909; in kafir corn and milo maize, 4,188 acres; in wheat, 2,382 acres; in corn, 1,034 acres; and in oats, 574 acres. About 15,000 orchard fruit trees were enumerated, and about 3,000 grape vines. In 1903 Castro County had an assessed valuation of $864,157; and in 1913, $3,289,433.