Portland was first settled in the early 1800s as one of the first settlements along the Rideau Waterway. The original seven houses in Portland, informally known as "The Landing", were a transfer point for passengers travelling from Brockville and continuing by barge to Perth.

With the completion of the Rideau Canal Waterway in 1832, steamboats and barges carrying raw materials such as cordwood, maple syrup, potash, cheese, tanned hides and salt beef were a common sight. Portland became a thriving village of trade with Kingston, Montreal and Ottawa.

The village of Portland took its name in 1843 from William Cavendish-Bentinck, 3rd Duke of Portland. By the 1860s, the settlement had expanded considerably to require five hotels and, by the early 1900s, cottages were springing up around the lake and the tourist trade had begun. Advances in rail and road travel and increasing tourism offset a decline in the role of agriculture in the economy of Portland. Tourism then began to lead the economy of Portland, and still does to this day.

An international speed skating tournament called Skate the Lake is held each winter by Portland Outdoors on the Big Rideau Lake at Portland.