After the Utes were expelled from the Gunnison and Uncompahgre river valleys in 1881, town builders, ranchers, and farmers arrived. Delta County was created one year later but developed slowly without the inducement of gold or silver. Slow growth meant a more stable population than those of the mercurial mining counties. Between 1900 and 1910, an irrigated farming boom roughly doubled the population to 13,000. Since then the county has grown slowly, reaching a population of 20,980 in 1990.

The Denver & Rio Grande Railroad, which built from Gunnison through Delta County to Grand Junction in 1881–1882, instigated the founding of many towns, including Delta, Hotchkiss, and Paonia. Along Surface Creek, the orchard towns of Austin, Cedaredge, and Eckert emerged. After 1900 cattle ranching became less important than irrigated farming. Irrigation enables Delta County to produce two-thirds of the state's apple crop, as well as apricots, cherries, nectarines, peaches, and plums.

To augment its agricultural base, Delta County has courted tourists, taking advantage of nearby Grand Mesa and the Black Canyon of the Gunnison National Monument. Big game hunting is another major draw, as locals and outsiders load up for elk, mule deer, and bear. The small towns of Delta and Paonia, which celebrate their heritage with lively murals and museums, have attracted refugees from urban areas.