This article examines the distribution of the five linguistic features that were used by Luis F. Lindley Cintra (1971) to establish his widely accepted classification of Portuguese dialects. The main objective of this study is to assess the internal consistency of Cintra’s proposal and its validity in modern Portuguese. The network of this analysis has 143 points in European Continental Portuguese and uses unpublished materials from the Atlas Linguístico-Etnográfico de Portugal e da Galiza. In order to produce a more accurate account, a new methodological approach is proposed: the utilization of a sizable corpus (194 questions and 20486 answers) and quantitative cartography yields a more dynamic picture of the dissemination of linguistic change and the vitality of dialectal features. The results of this analysis reveal several inconsistencies in Cintra’s proposal that are not due to diachronic developments but to the limitations of traditional dialectology and opaque data selection. This article demonstrates that certain dialectal features are present, even today, in a wider area than has usually been attributed to them in dialectological literature. The maps obtained in this study also show the main areas of occurrence for each phenomenon; thus, it is possible to track the routes of linguistic change and to infer future developments.