For the ‘Rotterdam Project’, a large amount of historical data on patrons of Rotterdam’s main theatres during the ‘long’ 19th century (1773–1914) was collected, digitally registered and statistically analysed. The data was gathered from the theatre archives of the city of Rotterdam and included data on such specifics as ticket sales, repertoire and featured performers. The database holds prosopography information on over 16,000 patrons and almost 15,000 registered ticket sales to these patrons. This dataset (https://doi.org/10.21943/auas.7381127) can be used to make comparisons to the datasets of similarly sized cities in other countries during the same period and for broader research on 19th-century cultural history. So far, the data has been mainly applied to empirically test the master narrative of theatre historiography on the social composition of theatre audiences. The analyses based on the data show that this narrative must, for the most part, be rejected.