The population of the county is well over 250,000 persons with population densities ranging from 3 persons per km2. to more than 800 persons per km2. This is due to the varied rainfall and terrain with the lower zones receiving an average 440 mm of rain per annum and the highland areas receiving up to 1900 mm of rain. The range rises in altitude from 500 m above sea level to almost 2,300 m at vuria peak which is the highest.
The county covers an area of 17,083.9 km2. of which a bulk 62% or 11,100 km2. is within Tsavo East and Tsavo West National Parks. The remaining 5,876 km2 is occupied by ranches, sisal estates, water bodies such as Lakes Chala and Jipe in Taveta and mzima springs, and the hilltop forests which occupy less than 100 km2. or approximately 10 km² out of 587.5 km².