It has been difficult to get people to recognize that the Patlachique phase (c. 100–1 BCE) was more than a prelude to the development of Teotihuacan. Art historian Esther Pasztory (1997) doesn't even mention it. Yet it was during the Patlachique phase that, in one or two centuries, Teotihuacan grew from almost nothing to become a large city. The area of fairly dense Patlachique sherd cover extends over 6 to 8 square km (Figure 4.1). By the end of this phase, the population was likely at least 20,000. Teotihuacan was now comparable to the population of Cuicuilco at its peak, if not larger. The TMP ceramic analysis, carried out in the 1960s, classified about 27,500 sherds from the surface collections as Patlachique. Areanalysis supervised by Evelyn Rattray in the 1970s classified about 42,300 as Patlachique – a 61% increase, but this is probably in error. Only another analysis of a selected sample (possible only because Millon insisted on saving all the TMP collections) can resolve this discrepancy. Fortunately, Sugiyama and Cabrera (2007) recovered a large quantity of stylistically homogeneous ceramics from the fill of Stage One of the Moon Pyramid, enabling a much clearer definition of the Patlachique ceramic complex, which can be the basis for this re-reanalysis.

Highest densities of Patlachique ceramics were collected by the TMP in a broad area around the eastern and northern slopes of Cerros Colorado and Malinalco. Patlachique sherd cover, probably light, extends an unknown distance west and north beyond the TMP map. Millon was constrained by NSF reviewers in the 1960s who did not recommend funds to extend his map beyond the limits of the Early Classic city.

This western Patlachique-phase settlement might be seen as a logical development from the sparse Cuicuilco tradition occupation on these hill slopes. However, the Cuicuilco tradition village near the wetlands below the springs (TF-35) was nearly abandoned.