Did you know that for decades, the beginning of the northern frontier was marked by the end of a tarmacked road? The point at which the roads ended was called Archer’s post and is today the end of Isiolo county. Ewaso Nyiro River is currently the border marker of Isiolo County. While the river is reduced to a stream for the better part of the year, its might is pronounced when rains descend on Mt. Kenya. The river cannot be navigated.