It was named for Robert Anderson Irion. The county embraces 1,051 square miles of rolling prairie, grass, mesquite, and, in some sections, exposed rock. Elevations range from 2,100 to 2,600 feet above sea level.
Soils vary from sandy to clay to gravel.
The average annual rainfall is 21.33 inches. The growing season lasts 232 days. Oil and gas production provides most of the county's income. The Tonkawa Indians once occupied the area of Irion County. From 1858 to 1861 coaches of the San Antonio-San Diego Mail and the Butterfield Overland Mailq qv crossed the region.