Northumberland role in the Industrial Revolution from the 18th century on. Many coal mines operated in Northumberland until the widespread closures in the 1970s and 1980s. Collieries operated at Ashington, Bedlington, Blyth, Choppington, Netherton, Ellington and Pegswood. The region's coalfields fuelled industrial expansion in other areas of Britain, and the need to transport the coal from the collieries to the Tyne led to the development of the first railways. Shipbuilding and armaments manufacture were other important industries before the deindustrialisation of the 1980s. Northumberland remains largely rural, and is the least-densely populated county in England. In recent years the county has
Maine people per square mile, making it the least densely populated state in New England, the American northeast, the eastern seaboard, of all of the states with an Atlantic coastline and of all of the states east of the Mississippi River. The mean population center of Maine is located in Kennebec County, just east of Augusta. The Greater Portland metropolitan area is the most densely populated with nearly 40% of Maine's population. Portland's estimated population in 2016 was 66,937. As explained in detail under "Geography", there are large tracts of uninhabited land in some remote parts of the interior. Maine has