The city of Mahendragarh was formerly known as Kanoud because of Kanauadia populated by Brahmins. It is said that Malik Mahadud Khan, a servant of Babar had settled. In the seventeenth century, Maratha ruler Tanti Tope built a fort here. In 1861, ruler Maharaja Narendra Singh of Patiala principality had named this fort in Mahendergarh in honor of his son Mohinder Singh. Because of the name of the fort, this town came to be known as Mahendragarh and the name of Narnaul Nizam was changed to Mahendragarh Nizam.
In 1948, the district of Mahendragarh was formed with the part of Narnaul and Mahendragarh tehsil of Patiala principality, Dadri (Charkhi Dadri) tehsil of Jind principality and the part of the Nizam of Nabha, and Narnaul was made the district headquarters. It is noteworthy that Mahendergarh district is the only district in the state, whose district headquarters is not in line with the name of the district but located in Narnaul.
Since the formation of Mahendergarh district in 1948, due to the reconstruction of the districts and the formation of new districts, the geographical boundaries of Mahendergarh have been changed many times. After making the new district of Rewari in 1989, the geographical boundaries of Mahendergarh district have changed.
The district is divided into three sub-divisions: Narnaul, Mahendragarh and Kanina, which are further divided into five Tehsils : Narnaul, Ateli, Nangal Chaudhary, Mahendragarh, Kanina and 1 Sub Tehsil: Satnali. There are four Vidhan Sabha constituencies in this district: Narnaul, Ateli, Nangal Chaudhary, Mahendragarh. All of these are part of Bhiwani-Mahendragarh Lok Sabha constituency.
Mahendergarh district is situated at the extreme end of the south-west end of Haryana state. Its west-south borders and a large part of the eastern boundary, the Rajasthan region and the rest of the eastern boundary, along with the districts of Haryana, Rewari and northern part of Bhiwani district.
The total area of this district is 1899 square kilometers. In this, the total area of Narnaul sub-division is 922.34 square kilometers and the total area of Mahendergarh and Kanina sub-division is 976.66 square kilometers. The number of villages in Mahendergarh district is 374.
The area of Mahendergarh district is dry due to its sandy and mountainous areas. Therefore, the climate here is cool in summers and hot in winter. Due to the adjoining Rajasthan border, there are strong winds and dusty storms in the district during the summer. Apart from the rainy season, there is also some rainfall in the month of February and March in the autumn.