The Local Government Act 1972 (c. 70) is an Act of Parliament in the United Kingdom that reformed local government in England and Wales on 1 April 1974.
Its pattern of two-tier metropolitan and non-metropolitan county and district councils remains in use today in large parts of England, although the metropolitan county councils were abolished in 1986, and both county and district councils were replaced with unitary authorities in many areas in the 1990s.
In Wales, too, the Act established a similar pattern of counties and districts, but these have since been entirely replaced with a system of unitary authorities.
In Scotland, where this Act did not apply, the Local Government (Scotland) Act 1973 regionalised local government with a system of two-tier regions and districts in 1975 – this was also replaced by a system of unitary council areas in 1996.
Elections were held to the new authorities in 1973, and they acted as "shadow authorities" until the handover date. Elections to county councils were held on 12 April, for metropolitan and Welsh districts on 10 May, and for non-metropolitan district councils on 7 June
More information on the Wikipedia page