Manchester
The first city built by industry rather than for it.
Kernel
Manchester is the place where the Industrial Revolution becomes a city. Cottonopolis — 1.5 million spindles in 1830 — was the densest concentration of mechanized production the world had ever seen. The combination of damp climate (cotton spinning needed humidity), nearby coal, and proximity to the Liverpool slave-cotton port produced an urban form Engels and Marx walked through and called "the first manufacturing city of the world."
What it gave the world
The factory as a building type and as a social form. The trade union (Manchester is where modern unionism was forged). The Liberal economic doctrine that Britain ran on for a century (the Anti-Corn Law League was founded here, 1839). Engels's Condition of the Working Class in England (1845), the analytical text that became Marxism's empirical core. The Manchester Guardian (1821) as a model for the serious provincial press.
Why it declined
American cotton (after the Civil War, Indian and Egyptian alternatives), competition from Japan and later India in textile manufacture, the 20th-century shift of British manufacturing capital to services, and the 1970s collapse of the Lancashire mill economy. By 1980 the cotton industry was effectively gone. The city has since reinvented itself around services and education; the industrial pattern moved to Asia.