Archaeological findings and excavations of Qazvin plain approve the existence of settled societies (permanent-residence) and agriculture as well as show that its inhabitants had enjoyed primary industries and social order in the 7th millennium B.C. All of the residential quarters, temples, industrial workshops, ornamental objects, statues, and warehouses of grains etc. found in Qazvin show the civilization of the people of this land in thousands of years ago.

In the old writings of Europeans, Qazvin had been called “Arsas” or “Arsasia” and was named “Ragia” in the Greek writings as well.

The process of urbanization and development of housing in Qazvin after the spread of Islam over the city in 644 A.D. was so intensified that after a while the city was named as Babol Janat or the gate of paradise.

The extent of Qazvin in 867 A.D. can be understood from a narration of The Selected History (Tarikh Gozideh) which says that after carrying out the fortifications by Mousa Ibn Bougha, the city consisted of 206 towers and 7 gates.
Selecting Alamout as the headquarter for Ismailian Nazari and its subsequent cultural, political, and military challenges made Qazvin the focus of many important events of the country for about 200 years; accordingly the city had witnessed many massive military invasions and their devastating effects all the time.
At the time of Mogul invasion, the extent of the city was so vast that, according to Mostowfi‟s narration in Zafar Nameh, more than one million people had been living there. Qazvin regained its prosperity after a short period of recession in Ilkhanid era and according to tourists in Teimourid era, it had been the most cultivated and largest city after Samarqand in Iran.
Selecting Qazvin as the Safavid Capital in the 16th century A.D. in addition to magnifying the importance of the city brought about an excellent period of urban development which is observable in the writings of western ambassadors and merchants.
Even transferring capital from Qazvin to Isfahan in the 17th century A.D. did not make city fall into oblivion and until the end of Afsharian era we observe that a lot of magnificent edifices were made all over the city from which the splendid Naderi Veranda is to be named.
Throughout the Qajar era Qazvin was a self-ruled region connected to the Capital and in spite of its slight recession in economy and culture at that time, it was one of the active and flourishing centers of the country.
The heroic resistances of the people of this part of the country against the invasion of the savage and murderous Mogul troops as well as against devastating raid of Teimour, especially imposing the first defeat on Afghan invaders in Qazvin after the fall of Isfahan, demonstrate the undeniable role of the people of Qazvin in the history of the country. Public participation of people in anti-despotic constitutional movements is the beginning of a new period of the contemporary history in the country which continued till The Islamic Revolution happened in 1978 A.D.