As a whole, it used to constitute one district in previous administrations, which is now divided into six sub-counties and Constituencies; namely,
The county occupies an area of 26,744 km2.
Among the notable incident of Mandera history was the Rhamu Incident of the 1977 in which Somali military invaded Ethiopian defences from the Kenyan side in which a force of 1500 Somali soldiers attacked a border post, and killed 30 Kenyan police officers and soldiers.the Somali army successfully crossed into the Sidamo Region of Ethiopia in the so called Ogaden War.
As with the other areas of the North Eastern Province, Mandera is predominantly inhabited by ethnic Somalis. with the Garre clan representing majority of the population