Prior to the 1800s the area was home to various indigenous peoples for over a millennium, and in 1615 the famous explorer Samuel de Champlain traveled through the area as well.
In 1818 Adam Scott settled on the west shore of the Otonabee River. The next year he started building a sawmill and gristmill, and this established the area as Scott's Plains.
In 1822, the British Parliament had approved an experimental emigration plan to transport poor Irish Catholic families to Upper Canada. Three years later in 1825, Irish immigrants from the city of Cork began arriving in Scott's Plains.
Peter Robinson, a member of the Legislative Assembly of Upper Canada and a prominent businessman from York, Upper Canada, was the man who took on the emigration plan of 1825. Scott's Plains was renamed Peterborough in his honour.
In 1845, Sandford Fleming, inventor of Standard Time and designer of Canada's first postage stamp, moved to Peterborough.
In 1904, the Peterborough Lift Lock was completed, which has become a popular tourist attraction in the city. By this time, Peterborough had also become a highly industrialized city, and was one of the first places in Canada to generate hydro electrical power, even before Niagara Falls.