Seaham, United Kingdom

The marriage was short-lived, producing as its only child the mathematician Ada Lovelace, but it was long enough to have been a drain on the Milbanke estate. The area's fortunes changed when the Milbankes sold out in 1821 to the 3rd Marquess of Londonderry, who built a harbour, in 1828, to facilitate transport of goods from locally encouraged industries (the first coal mine was begun in 1845). However, this harbour later proved inadequate to deal with the millions of tonnes of coal and the 6th Marquess commissioned engineers Patrick Meik and Charles Meik to reclaim land and extend and deepen the dock. It was officially opened in 1905. The harbour is of particular interest because it consists of a series of interconnecting locks, rather than the more typical two wall construction.

As early as 1823, the 3rd Marquess had approached the architect John Dobson with a view to his drawing up plans for a town to be built around the harbour. Dobson did so, but the planned approach foundered for lack of funds, and the town instead grew in a more piecemeal fashion. To begin with, the town was itself called Seaham Harbour (to differentiate it from the ancient village); in time, though, the settlement as a whole came to be known as Seaham.

In 1853 John Candlish built the Londonderry Bottleworks in the town. It was the largest glass bottle works in Britain and survived until 1921. Candlish went on to become mayor and, in 1868, Liberal MP for Sunderland. Waste glass from the bottleworks was dumped at sea and is now washed up as glass pebbles, known as sea glass, on local beaches.

In 1928, production started at the last town colliery to be opened, Vane Tempest. By 1992, however, all three pits (Dawdon Colliery, Vane Tempest Colliery and Seaham Colliery – known locally as "the Knack") had closed, a process accelerated by the British miners' strike. The pit closures hit the local economy extremely hard.

Seaham Colliery suffered an underground explosion in 1880 which resulted in the loss of over 160 lives, including surface workers and rescuers.

Many local families were affected by the tragic loss of eight men and one boy in the 'Seaham Lifeboat Disaster', when the RNLI lifeboat, the George Elmy, foundered on 17 November 1962. To commemorate the event, the new coast road was named George Elmy Lifeboat Way.