Samyukta Maharashtra movement, which finally led to the state's creation, lasted for almost five years. Led by the Samyukta Maharashtra Samiti, which included the Communist Party, Praja Samajwadi Party, Peasants & Workers Party and Republican Party, its impact was such that the ruling party and the leaders were incapable of even responding.
A bill (proposed by the Father of the Nation himself) for the formation of linguistic regions was passed by Congress in 1920 at Nagpur. The British, for their administration convenience, merged regions without consideration for regional languages. There was a widespread public demand to amend the bill on linguistic basis.
Post-Independence, Congress came under pressure from the small but wealthy and influential business community in the port city to include it in Gujarat. The was a strong local demand for the formation of Maharashtra, including Mumbai, Goa, Belgaum, Karwar, Parbhani, Nipani and Varhad. The denial of this demand created the iconic movement, which still manages to capture popular imagination.
Three Centre-appointed commissions insisting that "the demand for linguistic region is useless and baseless and Maharashtra had no authority over Mumbai", a stand steadfastly held by the Bombay Presidency chief minister Morarji Desai, worked like oil on fire. In 1956, under the leadership of Keshavrao Jedhe, Samyukta Maharashtra Samiti was formed (earlier Samyukta Maharashtra Parishad). Acharya Atre, Prabodhankar Thackeray, Senapati Bapat, SA Dange and Shahir Amar Shaikh were active members of the samiti.
When the growing protests only saw more and more committees being set up, which kept sticking to the government's stand on carving out Mumbai for a lingusitic state, protesters became irate and their numbers began swelling. Desai ordered them to be fired upon, leading to the death of 106 martyrs.
The widespread anger that mounted made Congress capitulate and agree to the samiti's demand and, on May 1, 1960, Maharashtra was formed along with Mumbai. Goa, Belgaum and Karwar were kept out and this does lead to political heat during every election.