 Callahan County is included in the Abilene, TX Metropolitan Statistical Area.According to the U.S. Census Bureau, the county has a total area of , of which is land and (0.2%) is water.Callahan Divide is range of hills that extend twenty-six miles from west to southeast through Taylor and Callahan counties, with highest elevation 2411 feet, which together with other elevated areas in the two counties provide advantages in wind energy.