When India gained independence in 1947, Bengal was partitioned along religious lines. The western part went to Dominion of India (and was named West Bengal), while the eastern part went to Dominion of Pakistan as a province called East Bengal (later renamed as East Pakistan in 1956). The latter became independent Bangladesh in 1971.

In 1950, the Princely State of Cooch Behar merged with West Bengal.In 1955, the former French enclave of Chandannagar, which had passed into Indian control after 1950, was integrated into West Bengal; portions of Bihar were also subsequently merged with West Bengal. Both West and East Bengal suffered from large refugee influxes during and after the partition in 1947. Refugee resettlement and related issues continued to play a significant role in the politics and socio-economic condition of the state.

During the 1970s and 1980s, severe power shortages, strikes and a violent Naxalite movement damaged much of the state’s infrastructure, leading to a period of economic stagnation. The Bangladesh Liberation War of 1971 resulted in the influx of millions of refugees to West Bengal, causing significant strains on its infrastructure.The 1974 smallpox epidemic killed thousands. West Bengal politics underwent a major change when the Left Front won the 1977 assembly election, defeating the incumbent Indian National Congress. The Left Front, led by Communist Party of India (Marxist), governed the state for the subsequent three decades.