Explanation:

 After independence the Chief Commissioner's province of H.P. came into being on 15 April 1948. Himachal became a part C state on Sept. 1951 with the implementation of the Constitution of India. Himachal Pradesh became Union Territory on 1 November 1956. On 18 December 1970 the State of Himachal Pradesh Act was passed by Parliament and the new state came into being on 25 January 1971. Thus H.P. emerged as the eighteenth state of Indian Union.