The introduction of commensal rat (Rattus) species into Ontario is hypothesized to have followed the intensification of European settlement in the early to mid-19th century. However, the exact date of rat translocation is not precisely known. This study tracks the introduction and establishment of Rattus species across Lake Ontario, using archival newspaper accounts, and addresses the limited existing research on rats in Ontario. Rats are an important proxy in understanding early historic settlements and the historic relationships between humans and commensal or pest species. Rat-related accounts published in local newspapers, such as eradication methods or firsthand sightings, provide insight into the pattern of rat translocation. The archival accounts of rats suggest that they were introduced into the Kingston area in the early 19th century and into the Toronto area in the early to mid-19th century. This study examines the complex human-rodent interactions in colonial Ontario, highlighting the importance of conducting further archaeological research and radiometric testing of rodents in Ontario.