The ruler of Travancore was appointed as the governor (known as "Rajpramukh") of Travancore-Cochin. The Maharajah of Cochin was offered to be addressed as Uparaja Pramukh, but he did not want any title after handing over the power. The Maharaja politely said that the eldest member of Cochin Royal Family should be called Valiya Thampuran and gave up royal powers unconditionally for the good of the people. While Pattom A. Thanu Pillai was the Praja Socialist Party Chief minister in 1954, Travancore Tamil Nadu Congress launched a campaign for the merger of the Tamil-speaking regions of Southern Travancore with the neighbouring area of Madras state. The agitation took a violent turn and civilians and local police were killed at Marthandam and Puthukkada, irreparably alienating the entire Tamil-speaking population from merger into Travancore-Cochin.
Under State Reorganisation Act of 1956, the four southern taluks of Travancore, namely Thovalai, Agasteeswaram, Kalkulam and Vilavancode and a part of the Chencotta Taluk was merged with Madras state. On 1 November 1956 Travancore-Cochin was joined with Malabar District of Madras state to form the new state of Kerala, with a governor, appointed by the President of India, as the head of the state instead of "Rajpramukh".