Gampaha district which was declared as a new administrative district in 1978 was separated from Colombo district in that era. This district in extent of about 1387  SQ. K.M. is bounded as follows :

North   : Ma Oya

East     : A line drawn across Methirigala Mountain      

South   :  Kelani River

West    :  Indian Ocean

 and also, Gampaha district is bounded by Kurunegala and     Putlam districts from north, by Kegalle district from east and by Colombo district from south. According to the geographical situation, this district belonged to coastal plain, shows plain geographical characteristics in most of the area and mountainous geographical characteristics in northern and eastern parts of the district.