It is difficult if not impossible to imagine the 20th century without concrete. Surely the landscape of modernity and modernization would be unrecognizable without it. By 1900 concrete may indeed have been considered modern, but as pointed out by technical manuals throughout the century, it was by no means a new material. Ancient builders put it to use, most notably the Romans, who built walls (faced with brick) and arcuated spans (the 145-foot span of the Pantheon’s dome the most famous and well-preserved example). This classical pedigree appealed to many architects of the early 20th century, although modern concrete practice had more recent origins. Europeans experimented with it in the 18th century, when the English engineer John Smeaton used a form of hydraulic cement (a cement that hardens underwater) to rebuild the wall and lighthouse at Eddy-stone off the Cornwall coast in 1756. The French began their own experiments some 30 years later, using a combination of clay and cement fr...