The contribution provides a general outline of the Trieste civil registry office and population censuses, carried out by the Trieste municipal authorities in the period 1859–1875. It describes the modernization of the procedure for providing an overview of the population influx and related issues (suffrage, the right to social security based on homeland affiliation, planned development of urban infrastructure, etc.). The groundwork was done in the 1860s through the establishment of a modern civil registry service, with its organization lifted to the European level in the mid-1870s. The population census, carried out by the above-mentioned authorities in 1875, represents the peak of these endeavours, crowned with a comprehensive statistical publication. A turn of events after 1880 led to the gradual abolition of the system and a return to its predecessor.