[9][10][11] With prior military service, Sangma entered the political field in 1952, and subsequently was elected as the Chief Executive Member (CEM) of the Garo Hills Autonomous District Council (GHADC).
[citation needed] Though Wilson Reade, chairman of the Khasi National Durba, was the first one to demand a separate hill state, it was Sangma who accelerated the movement successfully.
When the Assamese language bill was passed in spite of opposition from tribal people later, he resigned from the cabinet to fight for the cause of separate statehood.
[2][12] In 1960, the Assam Provincial Congress Committee(APCC) met on 22 April 1960, and directed the Chief Minister Chaliha to declare the Assamese as the State language.
Under the leadership of Sangma, APHLC met Jawaharlal Nehru, Prime Minister of India, in November 1960, and raised the apprehensions of Assamese language on Tribals.
When the delegation met Nehru again in December 1960, Nehru offered a Scottish plan—full authority for tribals in internal matters and complete control over expenditures and freedom in regard to the language – it also has a constitution of the committee in the Legislative Assembly of Assam comprising all the MLA's from the hills to examine the legislative proposals for the hill areas.
[citation needed] In 1963, the Mizo Union revolted its stand against APHLC as they felt their individuality would be lost by joining the Khasis and the Garos.
With bitter opposition from APCC faction opposed to Chief Minister Chaliha, the committee was not constituted to work out the details of the Federal scheme.
Instead, a joint discussion in Delhi on 7 July 1967, with representatives from various political parties of the Plains and the APHLC was called, to make an effort to reach an agreed solution for the reorganisation of Assam.
APHLC boycotted the commission as it not only opposed the Federal idea, but also resigned all the seats it held in Khasi, and the Garo hills on 25 May 1968.
The Mikir and the North Cachar Hills districts were given the option to join the Autonomous state—they decided to stay within the Assam state.
To counter the influence gained by HSPDP in certain areas, All Party Hill Leaders Conference requested PM on 3 September 1970, to declare Meghalaya as a full-fledged state.
[citation needed] The peace in then autonomous districts of Assam was disturbed when the state administration decided to impose Assamese language as the state language using The Official Languages Bill on 18 October 1960 threatening the tribes, who were apprehensive of losing their culture and identity; consequently, he feared that the Assam government's linguistic policy would militate against the ethnic identity of the hill people and hence, he led the agitations that resulted them an autonomous status under the "Assam reorganisation (Meghalaya) Act 1969" until it became a full-fledged state on 21 January 1972.
[15] With realisation of Meghalaya as a state, it ultimately united the areas of the Khasi, Jainta, and the Garo Hills under the leadership of Williamson Sangma.
He being one of the major leaders of the hill statehood movement, he always craved for a better deal for the Garos, who were economically worse off than their Khasi-Jainta brethren.