In census it is very important to have clear demarcation of administrative boundaries so that the data can be tabulated and presented in line with existing administrative units. It is also crucial to have detailed segregation of rural and urban units down to the lowest level. Census data is universally presented in separate rural urban frames for comparisons as well as gauging development patterns. In W.Bengal rural units comprise of villages as the lowest unit which are coming under a Community Development Block or, simply, Block. Total number of Blocks in a district make up the total rural frame of the district There are 341 Blocks in W. Bengal under the rural frame as in Census of India, 2001. The largest number of Blocks are in Medinipur district with 54 while Dakshin Dinajpur has the lowest number of 7 Blocks. The urban units consist of statutory towns like Municipal Corporations, Municipalities, Notified Areas and Cantonment Boards. In West Bengal there are 6 Municipal Corporations, 113 Municipalities, 3 Notified Areas and 1 Cantonment Board. Apart from statutory towns there are also non statutory urban areas which are basically census creations according to certain geographic and economic parameters. Such urban areas are called Census Towns (CT). As per the urban frame of West Bengal for 2001 there are 252 Census Towns with highest number of 55 in Barddhaman district. There is another urban concept in Indian census called an urban Outgrowth (OG) which is basically extension of the urban facilities beyond the statutory limits of a Municipal Corporation or Municipality. In West Bengal there are 30 such urban outgrowths attached to equal number of statutory towns with the highest, 9, in Nadia district. Finally the urban frame in Indian census also has the concept of Urban Agglomeration (UA) which is a continuous and unbroken urban spread cutting across municipal or other urban limits and can be a combination of more than one statutory towns / census towns / outgrowths. There are 21 Urban Agglomerations in West Bengal with the highest number of 5 again in Nadia district. But it is the biggest and largest Kolkata UA that cuts across the district boundaries of North 24 Parganas, Nadia, Haora, Hugli and South 24 Parganas while other UAs are restricted to within the district boundaries.