A city at the junction of the rivers Avon and Frome. It is not recorded before c.1020, but by 1066 was a flourishing port. The Normans built there one of the key strategic castles of England. By 1216 Bristol was influential enough to have an elected mayor. In 1377 it ranked in the poll tax as the largest provincial town after York; its importance was recognized in 1373 when the king made it a county corporate; later its status was further enhanced when it became a cathedral city (1542). Bristol enjoyed a golden age in the late 17th and 18th cents. Its wealth came chiefly from transatlantic trade (especially in slaves) and its associated new industries (sugar and tobacco). By 1800, however, it was overtaken in importance by Liverpool, Manchester, and Birmingham. In the 1830s and 1840s I. K. Brunel helped to make Bristol an important terminus for railways and for Atlantic steamships, and from 1868 new docks at Avonmouth helped the city recover prosperity.