The National Reserve was first established in 1948 when the Mara Triangle, a 520 square kilometre area between the Siria escarpment, the Tanzanian border and the Mara River, was declared a National Game Reserve. The primary aim of the national reserve was to protect the spectacular wildlife in the ecosystem. In 1961, the reserve was brought under the control of the County Council of Narok and the core area was extended to the east to encompass an area of 1, 831 square kilometres. In 1984, parts of the reserve were set apart to provide access to watering points for livestock and the reserve was brought to its present size of 1, 510 kilometers. In 1995, following the creation of the Trans Mara District, the management of the Reserve was split between the County Councils of Narok (CNN) and County Council of Trans Mara (CCTM). CNN was responsible for the reserve to the east of the Mara River while CCTM was responsible for the reserve to the west of the river (also known as Mara Triangle). However, after the promulgation of the new constitution, the two county councils were defunct by the Narok County Government, which is now responsible for the management of the entire reserve.