English idiom

Taking, bringing or carrying coals to Newcastle is a phrase for the act of doing something very obviously superfluous or unnecessary.

Newcastle-upon-Tyne is a city in northeastern England. This region has been a coal mining center for many centuries, and includes some of the earliest coal mines in the British Isles. In the year 1344, Edward III made a decree that all coal from the Durham and Gateshead side of the Tyne was required to pass through Newcastle for transport. This really locked in the city's fate as a fuel center for the entire kingdom. The coal from Durham, Northumberland, Nottingham, Derbyshire and Wales was shifted to the massive Tyneside coal pits for transport.

The proximity of good shipping facilities on the Tyne River allowed easy transport of goods. The phrase dates back as far as 1538, by which time Newcastle was a major port for the shipping of many sorts of cargo. The coal which made its way through the Tyne ports was the the fuel for the Industrial Revolution. Newcastle-Upon-Tyne became a linchpin in the great growth boom that the British Empire enjoyed in this period.

Hirsch, ED, Kett, Joseph F and Trefil, James, eds. “The New Dictionary of Cultural Literacy,” Third Edition (Houghton Mifflin, 2002).
North East England History Pages www.thenortheast.fsnet.co.uk
Hancock, Roland, "Two Cities, One River - Newcastle and Gateshead Heritage Trail" in 24 Hour Museum, January 12 2005, http://www.24hourmuseum.org.uk/trlout_gfx_en/TRA23395.html
Causey Arch, information about the wagonway that helped bring coal to the Tyne river at: http://www.timarchive2.freeuk.com/html/body_causey.htm
This is the Northeast, Communigate, sponsored by Northumbria University: http://www.communigate.co.uk/ne/squashed/page3.phtml