The Township of Cavan, located in the United Counties of Northumberland and Durham (previously Durham County), was first surveyed in 1817 by Samuel G. Wilmot (who also surveyed North Monaghan and Smith Townships). The land which was to become Cavan Township was virgin forest, untouched by Europeans, and no longer considered Indigenous territory. Wilmot was assisted by John Deyell, who, with James Deyell were two of the first settlers in Cavan Township. They established a mill on a brook in 1824, and as a result, were the founders of the village of Millbrook. John Deyell was also responsible for the name of the township, Cavan County, being a neighbour of Monaghan County, the County in Ireland from whence he came. Cavan Township was settled quite quickly. The same year it was surveyed, 115 lots were ticketed. By the next year, 1818, a further 160 lots were ticketed. The total population of the township in 1819 was 244. Many of the pioneer settlers of the new township were either military men who were given land grants for their services in the War of 1812, or Irish emigrants, many who were from County Cavan in Ireland. In 1825, the population reached 936; ten years later, in 1835, the population had more than doubled to 2,575. Cavan continued grow, and its population peaked in 1861, at 4,901.