London grew along with its nation's prosperity, which was due partly to the national benefits of freer trade (repeal of the 'corn' (grain) laws in the mid-century), partly to industrialization and related exports, and partly to the conquest of great portions of the world and commercial hegemony over a good fraction of the rest. Manchester grew as a cotton processing center, benefiting first from slave-harvested plantations in America, and then from British India, where local cotton processing was banned. Birmingham prospered, and grew, as it cashed in on its industrial innovations from the prior century. Glasgow grew as it was linked to iron and coal by canal, and to the sea by dredging and deepening the River Clyde.