The area was historically inhabited by
Mississaugas First Nations. After the Rice Lake Treaty #20 was signed in 1818, in which of land north of Rice Lake were surrendered, both Douro and Dummer townships were opened for settlement. Douro Township was named in honour of one of the battles in the
Peninsula War. In 1823, Dummer Township was surveyed, and in 1831, 2,000 Irish and English settlers arrived there to begin colonization, who were granted of land per family. In 1841, the first post office in Dummer Township opened. By that time, both townships were fully settled. == Demographics ==