The ancient trans-isthmus roadway known as the diolkos has been central to Roman Corinth’s commercial image since the mid-19th century. Remarkably, however, there is little textual or archaeological evidence for the commonly held view that the Isthmus functioned as a regular thoroughfare for ships and cargoes in the Early Roman era. In this paper, I argue against the regular use of the diolkos road for transshipment of goods in the first century AD and propose a different way of conceptualizing the commercial facility of the territory. The Isthmus was not so much a thoroughfare like the modern canal, but rather, a central mart, entrepot, and emporium for the importing, exporting, and redistribution of goods. While the urban center was obviously tied to the region’s commercial economy, the emporium subsisted in the major harbors of Kenchreai and Lechaion. The construction of large-scale harborworks in the first and second centuries signal the growing imperial and local interest in developing the commercial apparatus of the Roman city.