In the third chapter of Helaman, we read that the Nephites became expert in using cement to construct houses as well as entire cities. As he abridged portions of the Nephite record several centuries later, the prophet Mormon pinpointed 46 BC as the year of Helaman’s declaration. No one in Joseph Smith’s day—in fact, no one in the nineteenth century—could have known that cement began to be used extensively in Mesoamerica around this time. Found in the Valley of Mexico, the oldest-known concrete has been dated at approximately 200 BC, after which—and especially after AD 200—cement was used on a broad scale, as exemplified at the immense ruins of Teotihuacán near Mexico City. (See Echoes, 287–288.)