In this paper, we are exploring the history of the genitive alternation (of-vs. s-genitive) in Singapore English based on corpus data covering both British English (as the historical input variety) and Singapore English (as the target variety whose diachronic development we are interested in). Specifically, while earlier research has produced partly diachronic accounts of genitive variability, the diachronic development of the genitive has so far not been studied in ESL contexts, a gap which this study attempts to fill. Nearly 6000 instances of of-and s-genitives were annotated for a large number of predictors including phonetic variables (e.g. final sibilancy of possessor), semantic variables (e.g. animacy of possessor/possessum), syntactic variables (e.g. length of possessor/possessum), and pragmatic variables (e.g. discourse accessibility of possessor/possessum). We then applied the method of Multifactorial Prediction and Deviation Analysis with Regressions/Random Forests to the data to explore (i) how genitive choices in Singapore English differ from those in British English and, after a methodological interlude, (ii) how genitive choices changed over time in Singapore English. We conclude with some important recommendations regarding diachronic studies of structural nativization and their theoretical implications in models such as those of Moag (1982) or Schneider (2003, 2007).