Using the Princeton nuptiality index Im, we analyzed historical developments in the proportion of married women of reproductive age in Spain. We show the internal diversity in nuptiality patterns and offer an explanatory statistical model based on panel data analysis to identify the main variables influencing these changes over more than a century (1887–1991). We found that Spain has been the developed country with the greatest contrasts in its provincial nuptiality patterns (measured by Im), although this diversity has lessened over the course of time. We also found that some socioeconomic variables (the gross domestic product per capita and the percentage of population living in cities) do not have a linear relationship with female nuptiality but rather have a U shape or an inverted U shape. This may partly account for some of the controversy that has raged on this topic over the past few decades on an international level.