The district had only one local authority, Trans Mara county council.
Under the 2010 Constitution of Kenya and the new devolved form of government, the Trans Mara area was merged into Narok County.
It continues as the Kilgoris Constituency electorally and administratively.
Its name refers to the territory "across the Mara River" from the perspective of the rest of Narok County.
The term "Trans Mara" is still used to refer to the geographical area.