The name "Sanandaj" is the variant of the Kurdish name "Sinedijh" (Sine fortress). Sanandaj is a rather new city and was built less than 400 years ago by the Ardalan principality in 17th century. After the Islamic conquest in AD 642 , majority of the inhabitants accepted Islam. Today most inhabitants follow Sunni Islam which is the predominant religion. This differentiates this area from most of Iran which is primarily Shi'ah.
Suleyman Khan Ardalan the governor of the region constructed the Sine dijh (castle) during the Shah Safi period (1629-1642). Sanandaj was under the control of the Ardalan household for four centuries. In the war between the Safavids and the Ottomans, this family sometimes sided with the Safavids and sometimes with the Ottomans. In 1733, Karim Khan Zand destroyed Sanandaj. After a period of chaos, Khusrow Khan Ardalan took over power in this part of Kurdistan. From 1799 to 1824, Amanolah Khan Ardalan, son of Khusrow Khan Ardalangoverned, ruled in Sanandaj. He worked to build up and inprove Sanandaj. In 1867, due to the dissatisfaction of the inhabitants, Haj Mirza Mu'tamid-u-lleh, the uncle of Nasser-al-Din Shah, came to power. He governed in the region until the year 1874.
The main landmark of Sanandaj is a fortress dating back to the period of Abbasid rule. Sanandaj was very prosperous in the Safavid era but was completely destroyed at the time of Karim Khan of the Zand dynasty. It was later chosen to be the capital of this province and is presently one of the most prominent cities of western Iran.
Tracing their roots to the village of Kilaneh, the Sanandaji family, which since the Islamic Revolution in 1979 have moved to Europe and the United States, were the predominant land and farm owners in the state of Kurdistan throughout its modern history. Until the White Revolution during the Shah's reign, the family heavily influenced the economy and society of the region. It is for this reason that they bear the title of Khan, and the name Sanandaji.
The Founder of the Sanandaji family, Kohzad (the son of mountains) was the son of Bahram who was the son of Khodadad born 1660 A.D. in Kilaneh, situated 20 Kilometers south of Sanandaj. Kohzad migrated to Sanandaj around 1750, setting up a modest cloth trading business which his sons followed up. By the end of the 18th century the family was wealthy enough to become one of the most influential landowners in the then largely feudal society of Persia.
A sizable Jewish minority settled down and thrived in Sanandaj due to the tolerant attitude of the Kurdish citizens plus the support of the ruling elite. A great majority of this Jewish community migrated to Israel by the end of 1980s.