Everything valuable that economics textbooks describe as a "public good" has, at one time or another, been provided on the market by individuals and private firms. Even today, capitalists and entrepreneurs are rebuilding public spaces in Detroit, positive externalitites be damned:
Whether or not they’re expecting to profit, Gilbert and other capitalists — large and small — are trying to rebuild the city, even stepping in and picking up some duties that were once handled by the public sector. Shop owners around the city are cleaning up the blighted storefronts and public spaces around them. Only 35,000 of Detroit’s 88,000 streetlights actually work, so some owners are buying and installing their own. In Gilbert’s downtown, a Rock Ventures security force patrols the city center 24 hours a day, monitoring 300 surveillance cameras from a control center. Gilbert is proposing to pay $50 million for the land beneath the county courthouse and a partly built jail near his center-city casino, with the intention of moving the municipal buildings to a far-off neighborhood; his goal is to clear the way for an entertainment district that flows south, without interruption, from the sports arenas past his casino and into downtown. Detroit’s new mayor, Mike Duggan, told me he had no problem with the private sector doing so much to shape his city: Other metropolises had their entrepreneurs and deep-pocketed magnates who built and bought and financed things. With a state-appointed emergency manager overseeing various aspects of Detroit’s operations, with many civic services inoperable for years and with a dire need for investment, Duggan said he felt lucky that his town was getting its turn.
Thanks to Craig Newmark for the pointer.