K. P. Viswanathan was born to parents Kallayil Pangan and Parukutty in Kunnamkulam on 22 April 1940, and graduated from Kerala Varma College, Thrissur, and the Government Law College, Ernakulam, then worked as a lawyer.
He won the 1977, and 1980, and 1987 Kerala Legislative Assembly elections to represent Kunnamkulam on behalf of the Indian National Congress.
He returned to the Kerala Legislative Assembly in 1987, 1991, 1996, and 2001, as a representative of Kodakara.
Viswanathan served twice as minister of forests and wildlife within the government of Kerala, in the fourth Karunakaran ministry in office between 1991 and 1994, as well as the first Oommen Chandy ministry from 2004 to 2005.
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