The area of the western Gulf of Corinth around the city of Aigio (Achaea, northwest Peloponnese, Greece) represents an international pilot site for continuous monitoring and multidisciplinary research on earthquake processes. In the framework of the ANR‐SISCOR Corinth Rift Laboratory project (2011–2014), a thorough reappraisal of the five largest (⁠Mw>6⁠) eighteenth–nineteenth century earthquakes was performed, namely those of 14 May 1748, 23 August 1817, 26 December 1861, 9 September 1888, and 25 August 1889. Written observations of earthquake effects were looked into in their original version and language and were placed in the context from which they originated, to avoid the translations and digests on which previous seismological studies had relied. Earthquake records were traced for 108 different localities, and 143 macroseismic intensities in European Macroseismic Scale 1998 (EMS‐98) have been assigned. Earthquake‐related geological phenomena have been identified and carefully mapped, to be used as a further constraint of the location and magnitude of the associated earthquakes. Finally, new parameters for the studied earthquakes have been assessed with two separate and independent strategies to quantify epistemic uncertainties. In conclusion, the 1748, 1817, and 1888 earthquakes were located in the area of Aigio; the 1861 earthquake is reckoned to be the largest in the area, with an epicentral location at sea; whereas the 1889 earthquake has been relocated to the northwest in mainland Greece, well outside the Gulf of Corinth.