The first settlers of European descent in the area then known as Erin Township were George and Nathaniel Roszel from Pennsylvania who arrived in November 1820; Nathanial acquired land in what is now Ballinafad. (Most of the settlers during the township's development were Scottish.) In 1821, William How and his family arrived from England and built a home in what is now Hillsburgh; he started the first general store in that community. The first Township Meeting was held on January 5, 1824; Henry Trout Sr. was appointed Town Clerk. The township halls have always been in or near Hillsburgh. The township population grew over the years from 1,368 in 1841, to 3,055 in 1850 when 15,400 acres were under cultivation. The urban community now called Erin developed after mills were built on the Credit River between 1826 and 1829. The first settlers included Daniel MacMillan and the Trout family. The settlement was established as "MacMillan's Mills" although most sources indicate that the Trout family built the first sawmill. Even so, Daniel MacMillan and his brothers are acknowledged as significant contributors to the growth of the village. By 1839 a post-office had opened. Records from 1841 indicate that the entire Township of Erin had a population of just 1,368. By 1846, the small settlement in the south-west of the township, then called McMillen's Mills, had a grist and saw mill, a tavern and blacksmith's shop but only 40 to 50 residents. In 1849, the first place of worship, the Union Church was being used by several denominations. Previously, services had been held in homes and in other available buildings. By 1851, the population increased to 300; the name of the settlement was Erinsville at the time but was later shortened to Erin. Businesses in the area included a distillery, a tannery, and carding, oatmeal and grist-mills. The river provided the power for mills, helping to boost agriculture, milling and wood products manufacturing. By 1869 the population was 600 and the post office was receiving mail daily. The
Credit Valley Railway reached Erin in 1879 and the same year, Erin was incorporated as a village. At the time the population was 750. Electricity from small private providers became available before 1890 and a formal power company was established in 1900, Cataract Light & Power. Hydro power was generated at Cataract, in Caledon, an area that is now in the
Forks of the Credit Provincial Park. That facility was sold to Ontario Hydro in 1944 and continued to operate until 1947. == Demographics ==