Borujerd is a city in Lorestan Province in western Iran. Among the existing modern cities in Iran, Borujerd is one of the oldest reported at least since the 9th century. In Sassanid Empire, Borujerd was a small town and region neighbouring Nahavand. Gaining more attention during the Great Seljuq Empire in the 9th and 10th centuries, Borujerd stood as an industrial, commercial and strategic city in Zagros Mountains until the 20th century. In its golden ages, Borujerd was selected as the state capital of Lorestan and Khuzestan region during Qajar dynasty in the 18th and 19th centuries.
Founded by the Jews had taken refuge in Persia, since the Muslim conquest of Persia (637-651), Borujerd has been considered as a strategic area and especially in Seljuq dynasty and Qajar dynasty it received significant attention and many mosques, schools, bridges and castles were made or rebuilt by these dynasties.
The Borujerd area has been populated at least since 3000 BC. Medes used its pastures to produce and train thousands of horses each year. However, it owes much of its development to the Jews who came to Persia after they had got close to extinction. Sassanid Empire promoted Borujerd to a city level and built a fire-temple there. During the Muslim conquest of Persia (637-651), Borujerd castle was used by the Iranian army to support the troops and the final battle occurred in Nahavand, 55 km north West of Borujerd. Yazdegerd III escaped to Borujerd castle and his army reunited again there. The Islamic Arab governor, Abudolf ibn Hamulah, rebuilt the city and constructed the Jameh Mosque of Borujerd on top of a Zoroastrian fire temple.
Seljuq rulers had many travels and battles in Borujerd and Barkiyaruq the sultan of Great Seljuk from 1094-1105 died in this city. Some references mention that Zavvarian 5 km N of Borujerd City is his tomb, however, according to history books, his body was returned to Isfahan.
From approximately 1000 to 1500, Borujerd Was governed by Atabakan-e Lorestan who governed Lur-e-Kuchak. Genghis Khan and Mongols attacked the Lur-e-Kuchak and ruined Borujerd and Khorramabad. Timur attacked Borujerd two times and destroyed this city but Timurids used Borujerd Castle and Roomian Castle for military purposes.
In Safavid era (1500-1700) Borujerd was governed as a separate state including Japlaq or Gapleh, and was neighbour of Golpayegan. Zand kings were Laks and originally from somewhere between Malayer and Borujerd. They paid attention to Borujerd for its brave soldiers (known as Silakhori) which were already used by Safavids. Several battles occurred there.
In Qajar era, Borujerd was a small state at first but changed to the centre of Lorestan Province and Khuzestan Province later and the city developed rapidly. The Soltani Mosque of Borujerd, the Great Bazaar of Borujerd and many schools and gardens were built and the city castle was rebuilt.
Reza Shah quit insurgencies of Lorestan and established army, railway, roads, hospitals and modern schools in Borujerd. In his time, Borujerd State was eliminated and according to new political dividing, Borujerd was attached to Lorestan Province.