Indian Constitution was drafted by the Constituent Assembly, which was elected by elected members of the provincial assemblies (389 member).
Constituent Assembly took two years, eleven months and eighteen days to complete its historic task of drafting the Constitution for independent India, during which, it held eleven sessions over 165 days. Of these, 114 days were spent on the consideration of the draft Constitution.
Key Members of Constituent Assembly
President: Dr. Rajendra Prasad, INC
Chairman of the drafting committee: Dr. B. R. Ambedkar, SCF
Vice Presidents: Harendra Coomar Mookerjee, V. T. Krishnamachari
Legal Advisor: B. N. Rau
Major Committees
Drafting Committee – Dr. B.R. Ambedkar
Union Powers Committee – Jawaharlal Nehru
Union Constitution Committee – Jawaharlal Nehru
Provincial Constitution Committee – Sardar Patel
Advisory Committee on Fundamental Rights, Minorities and Tribal and Excluded Areas – Sardar Patel
Source: Internet