FORTUNE — When Mayor Michael Bloomberg pledged to end New York’s overdependence on Wall Street, the city responded by becoming the country’s fastest-growing digital-technology hub. Despite less-than-stellar access to a reliable broadband network, New York now hosts over 1,800 tech companies. The city overtook Boston to become the country’s second-largest tech center, after Silicon Valley, this year. This map shows the Big Apple’s ecosystem of startups, venture capital firms, incubators, digital-media companies, and educational institutions.

This story is from the December 3, 2012 issue of Fortune.