In ancient times, Gilan region was divided to `the Caspian' and `the Golha' (flowers) subregions. Before the Iran's provincial divisions into the current state, Gilan was divided by the Sefid-Rud River into eastern and western regions. The river's eastern side called Biehpish and the western side Biehpas. At some point in time, Lahijan became the capital of Biehpish. This region has been one of Iran's major silk-producing centers as well as the country's first area for the tea-plantation set out by Prince Mohammad Mirza.
Prince Mohammad Mirza known as "Kashef-ol-Saltaneh" who was born in Lahijan was the first mayor of Tehran. As the Iranian ambassador to India under British rule, he knew the British would not allow him to learn about the secrets of tea production, as it was their biggest business in India at the time. So being fluent in French, the prince pretended to be a French laborer and started to work in the tea plantations and factories to learn how to produce tea. Ultimately his plan was to take back some samples of this tea to Iran to cultivate. He was successful in this endeavor only because of his diplomatic immunity which stopped the British from searching his secretly stashed sample. His mausoleum in Lahijan is now part of the "Iran Tea Museum".
The foundation of Lahijan is attributed to 'Lahij Ebne Saam'. Oljaito, the Mongol ruler conquered Lahijan in 705 AH. Then Amir Teimoor attacked this region. Finally, Shah Abbas I defeated 'Khan Ahmad' and thereafter the Safavid governors ruled this city. Amongst the unpleasant events in the history of this city were the outbreak of plague in 703 AH., the conflagration of 850 AH. and the conquest of it by the Russian army in 1725 AD. Lahijan was one of the main bases of the Jungle Movement.