From the Wikipedia page 
The Greater Accra Region has the smallest area of Ghana's 10 administrative regions, occupying a total land surface of 3,245 square kilometres,. This is 1.4 per cent of the total land area of Ghana. It is the second most populated region, after the Ashanti Region, with a population of 4,010,054 in 2010, accounting for 16.3 per cent of Ghana's total population.
The Greater Accra region is the most urbanized region in the country.
In 1960, Greater Accra, then referred to as Accra Capital District, was geographically part of the Eastern Region. It was, however, administered separately by the Minister responsible for local government. With effect from 23 July 1982, Greater Accra was created by the Greater Accra Region Law (PNDCL 26) as a legally separate region.
The political administration of the region is through the local government system. Under this administration system, the region is divided into 16 districts, as of June 2012 addition of 6 district areas. Each District, Municipal or Metropolitan Area, is administered by a Chief Executive, representing the central government but deriving authority from an Assembly headed by a presiding member elected from among the members themselves.