The Tay River was formed during the retreat of the Champlain Sea after the last ice age. The name given to it by the Mississauga First Nation, who controlled its territory at the time of the arrival of the first European settlers, appears to have not been recorded. They used its territory for hunting, especially in the winter, and likely harvested manoomin (wild rice) on some of its lakes, for instance Christie Lake. Early European settlers called it the Pike River; the name Tay replaced it at some time during the arrival of many Scottish settlers after the founding of the Perth Military Settlement in 1816, doubtless in reference to the River Tay in Scotland. The new name was already clearly established during the construction of numerous mills on the river in the 1820s, and the Tay Canal in the 1830s.