This in-depth study explores the technological, cultural, and mercantile factors behind the infrastructure that transformed early modern London. Beginning in 1580, a number of competing London companies sold water directly to consumers through a large network of wooden mains in the expanding metropolis. This new water industry flourished throughout the 1600s, eventually expanding to serve tens of thousands of homes. By the late eighteenth century, more than 80 percent of the city’s houses had water connections—making London the best-served metropolis in the world while demonstrating that it was legally, commercially, and technologically possible to run an infrastructure network within the largest city on earth. Historian Leslie Tomory shows how an explosion of consumer demand and new technologies imported from the Continent spurred the rapid growth of London’s water industry. Meanwhile, several key local innovations reshaped the industry by enlarging the size of the supply network. By 1800, the success of London’s water industry made it a model for cities across Europe and beyond. It even inspired builders of other large-scale urban projects, including gas and sewage supply networks.