<P> Shimla district has the largest urban population in the state at 25% . Notable government actions include a ban on polyethylene bags and tobacco products . A 2017 survey by an international organization ranked Himachal Pradesh India's least corrupt state . </P> <P> The history of the area that now constitutes Himachal Pradesh dates to the Indus valley civilisation that flourished between 2250 and 1750 BCE . Tribes such as the Koili, Hali, Dagi, Dhaugri, Dasa, Khasa, Kinnar, and Kirat inhabited the region from the prehistoric era . </P> <P> During the Vedic period, several small republics known as Janapada existed which were later conquered by the Gupta Empire . After a brief period of supremacy by King Harshavardhana, the region was divided into several local powers headed by chieftains, including some Rajput principalities . These kingdoms enjoyed a large degree of independence and were invaded by Delhi Sultanate a number of times . Mahmud Ghaznavi conquered Kangra at the beginning of the 10th century . Timur and Sikander Lodi also marched through the lower hills of the state and captured a number of forts and fought many battles . Several hill states acknowledged Mughal suzerainty and paid regular tribute to the Mughals . </P> <P> The Kingdom of Gorkha conquered many kingdoms and came to power in Nepal in 1768 . They consolidated their military power and began to expand their territory . Gradually, the Kingdom of Nepal annexed Sirmour and Shimla . Under the leadership of Amar Singh Thapa, the Nepali army laid siege to Kangra . They managed to defeat Sansar Chand Katoch, the ruler of Kangra, in 1806 with the help of many provincial chiefs . However, the Nepali army could not capture Kangra fort which came under Maharaja Ranjeet Singh in 1809 . After the defeat, they began to expand towards the south of the state . However, Raja Ram Singh, Raja of Siba State, captured the fort of Siba from the remnants of Lahore Darbar in Samvat 1846, during the First Anglo - Sikh War . </P>

When were many areas of punjab merged with himachal pradesh