This chapter investigates the hypothesis that Republican era builders integrated a long-standing tradition of thoughtful reasoning and invention with skilled workmanship to develop highly sustainable masonry materials, construction technologies, and engineering solutions. Vitruvius's emphasis on the importance of knowledge and expertise (scientia) in the development of architectural craftsmanship and technical skill (ars) seems to correspond to the modern concept of construction engineering. Builders’ accurate empirical knowledge of the various material characteristics is confirmed by their selections of building stones in the extant Republican era monuments. Durable concrete constructions in Rome apparently date to the second century. Observations of the compositions and material characteristics of the dimension stone of fifth- to second-century monumental constructions support Vitruvius's remarks about the development of Roman construction engineering.