This city is bordered by Semnan city from the south, Sari city from the north, Firouzkoh city from the west, and Damghan city from the east. Sangsar district had a military governorate before Shahrivar 1320, which included Dodangeh, Chahardangeh and other parts of Sari city. It is reminded that in the geographical culture of Iran which was published in 1329  This area comes with the current limits and specifications as Sangasar section. This district was upgraded to a city in August 2016. The area of Mahdishahr Sangsar is about 1100 square kilometers. The beautiful and cool city of Shahmirzad, which is one of the cities of Mahdishahr city, attracts many tourists in the summer to see the beautiful scenery and towering trees of this city.

The historical background of this city goes back to before Islam and even to the time of the Pishdadi dynasties. In Ferdowsi's Shahnameh, Sangsar is mentioned as Segsar or Segsar. Segsar and Seksaran are also mentioned in the national narratives and epics of Iran. Is. Segesaran is also mentioned in several places in Ferdowsi's Shahnameh. Among the Turanians voting against the Iran war: in the Shahnameh dictionary, it is mentioned under the word "Segsar" From the border and the smells that Dahyan took place in. And about Dahian, under the word Sekzi, we read " ... Dah were a group of Arians who settled in the Khorezm plain and then settled on the southern side of the Caspian Sea. The people of Bastowe came from... them. The king of Iran dispersed the Daeh group. A group of them moved to Zabulestan and they were called Sekzi... and the plain of Khwarazm was called Dahestan, which is an abbreviation of Dahestan, and now it is known as Dahestan. In this way, it can be said that Sangsar, which is located in the southern part of the Caspian Sea, is a part of the ancient Segsar, and the Sangsari are the survivors of the Dahians and are of the same race as the people of Sistan (Sajistan) and the old Khorezmians.