Before the national awakening period (pergerakan, 1880-1930), Javanese society was religiously homogenous with overlapping social identities and indistinct boundaries between them. Yet by 1930, there were deep social cleavages between groups. Archival material suggests that locally specific conditions in West, Central and East Java polarized society differently in each region: in West Java the primary divisions were between Christian/Muslim and Modernist/Traditionalist, in Central Java the divisions were similar but shallow and emerged late in the period, and in East Java only the Modernist/Traditionalist divide was salient. These different modes of polarization were then reflected in the policies of the emergent Islamic institutions Muhammadiyah, Nahdlatul Ulama and Persatuan Islam. Contemporary survey data demonstrates that regional differences endure in the attitudes of elites. These findings suggests that rather than using ideological or theological explanations for patterns of tolerance and intolerance, scholars examine the lived experiences of Islamic leaders within their local and historically rooted contexts.