<div> This paper examines register variation in Latin from the third century BCE to the fourteenth century CE using Key Feature Analysis (KFA) (Egbert and Biber, 2023), a quantitative method for identifying statistically over-and underrepresented linguistic features. Registers are defined as text varieties linked to communicative situations and characterized by distributions of lexico-grammatical features (Biber, 1988, 1995). Six dependency-parsed Universal Dependencies (UD) treebanks are classified a priori into ten register categories based on established scholarship. Additionally, Principal Component Analysis (PCA) is used to reduce dimensionality, in order to explore the texts major patterns of variation and clusters of linguistically similar texts. KFA reveals systematic register-specific grammatical profiles consistent with previous research (e.g. Biber (2014b)). Registers with involved language use (e.g. letters and speeches) show higher frequencies of personal reference and engagement, while philosophical texts favor subordination and impersonal constructions. Registers containing narrative elements (e.g. historiography, satire) contain high frequency of verbs in past tense. PCA places the charter register into a distinct cluster, while other registers form more closely grouped patterns. The strongest components reflect contrasts in number, aspect, tense and person, alongside subordination and cordination distributions. The results are largely confirmatory: KFA produces coherent and interpretable groupings of grammatical features consistent with previous findings, providing a proof of concept for quantitative register analysis in historical corpora. Data and code are openly available for future research. </div>