The Hillsborough River begins near the white sand beaches of the north shore and winds 45 km through rich farm country to its mouth (Charlottetown Harbour) on the south shore of Prince Edward Island. At its mouth, the North and West rivers come together to meet the Hillsborough. The Hillsborough is the largest river system on the island. French settlers called itRivière du Nord-Est and La Grande Rivière. The early colonial British named it Hillsborough for the Earl of Hillsborough. Local folk today know it as "The Road Straight Up."

Almost cutting the island in two from north to south, the Hillsborough River has always served as a "highway." For centuries, the Mi'kmaq fished and camped along its shores. Europeans settled here in the early 18th century, using the river for transportation and as a major shipbuilding area in the days of sail. There has been some commercial fishing in the river and today shellfish, particularly oysters, are harvested. The capital of Prince Edward Island, CHARLOTTETOWN, where the Fathers of Confederation met in 1864, is located at the mouth of the Hillsborough.

Due to the island's flat topography, for most of its length the Hillsborough is a tidal estuary with very little current. Its extensive salt marshes are rich breeding areas for thousands of marine birds and other land and marine animals. In 1997 the Hillsborough was designated as part of the CANADIAN HERITAGE RIVERS SYSTEM.