It was named for Stephen Crosby, qv a Texas land commissioner during the mid-nineteenth century. Most of the western half of Crosby County, flat land covered by rich loam, lies above the Caprock, qv and the eastern part of the county and its southwestern corner are broken country below the Caprock.
Drainage is to the forks of the Brazos River, White River, and numerous playas.
Vegetation includes mesquite, hackberry, cottonwood, cedar, catclaw, cacti, and grasses, particularly curly mesquite, grama, salt, and sage. Irrigated land totals 125,000 acres. Artifacts dating back 13,000 years to the early Paleolithic era have been discovered in Crosby County. The early people of the area were rovers who hunted and gathered plants and differed from neighboring peoples in weapons and tools. In more modern times the area of Crosby County was inhabited by the Comanches, mounted hunters and warriors who dominated much of the South Plains in the eighteenth and nineteenth centuries until their buffalo-based culture gave way to settlers and superior technology.