The Ottawa River, 1271 km long, chief tributary of the ST LAWRENCE RIVER, rises in a chain of lakes in the LAURENTIAN HIGHLANDS. It continues with Dozois Reservoir, Grand-Lac-Victoria, Lac Granet, Decelles Reservoir, Lac Simard and Lake Timiskaming, entering each slowly and discharging with a heavy rush. South from Lake Timiskaming, it grows broad and forceful, widening into marshy lakes, then constricting into turbulent rapids. At St-André-Est, the Ottawa expands to form Lac-des-Deux-Montagnes, from which it enters the St Lawrence through Rivière des Prairies and Rivière des Mille-Iles to the east, and by a channel to Lac St-Louis to the south. Tributaries from the north-side highlands are often wild and swift: DUMOINE RIVER (129 km), Coulonge River (217 km), Gatineau River (386 km), du Lièvre River (330 km), Petite Nation River (97 km) and Rouge River (185 km). From the south, the Petawawa River (187 km) and Madawaska River (230 km) also flow through rugged terrain, but the Mississippi River (169 km), Rideau River (146 km) and South Nation River (161 km) drain gentler land.

After the last glacier melted, it was the Ottawa that drained the Great Lakes until the land rose and a new channel was found via the St Lawrence. The fine clay soil of the southern valley was deposited by the Ottawa in its journey to the sea, forming a long fertile intrusion into the otherwise implacable Canadian SHIELD. From Lake Timiskaming to Montréal, the river forms the border between Ontario and Québec, but the division is more than political - to the south are rich farms and gentle hills, to the north the forests of the Laurentians.

For several hundred years, the Ottawa was the primary transportation route to the western interior. The Algonquin controlled it in early times and one group exacted tolls from a strategic base on Allumette Island, where they also grew corn and tobacco. They called the river "Kich esippi" meaning "The Great River". Jacques CARTIER probably saw the river from atop Mount Royal, but Étienne BRULÉ was likely the first European to travel it (1610). In 1613 via the Mattawa and FRENCH rivers to Georgian Bay, CHAMPLAIN travelled the route which was used to carry furs for the next 200 years. The river was a tough challenge for the voyageurs, requiring 18 portages, some of the most difficult being at Long Sault, Deschênes, Lac des Chats, Chenaux, Portage-du-Fort, Chaudière Falls, Rocher Fendu, Des Joachims, La Cave and Des Érables.

The French made small impact on the river valley, though they built a few posts and even drove some timber in the 1740s. L'ORIGNAL, granted in 1674, was the first seigneury in present-day Ontario but was not developed for 100 years. HAWKESBURY was founded in 1798, and there Thomas Mears built the first gristmill, sawmill and later the first steamer, the Union, on the Ottawa. The first paper mill in Canada was built 1803-05 at St-André-Est, and the American Philemon WRIGHT founded Wrightsville (later HULL) in 1800 with American settlers. Loyalists, led by Sir John JOHNSON, moved into the valley in 1814, and French settlers onto Petite Nation seigneury. In 1817 land along the Rideau River was granted to 1000 British veterans, and in 1825 Archibald MCNAB led a group of Scots to the mouth of the Madawaska River.

Log rafts descended the Ottawa even before it ceased to be the prime route of the fur trade after 1821. Wright showed that the route was feasible in 1807, and the British demand for pine grew until, by 1830, the valley timber trade dominated the Canadian economy. After 1850 the British demand for square timber fell, but in 1854 RECIPROCITY gained free access for Canadian lumber into the US market. The timber trade pervaded the social life of the valley. Armies of men lived in crude shanties during winter and descended on civilization with their rafts come spring. Competition among shanties and between French and Irish led to feuds and violent clashes (seeSHINERS' WARS). After the completion of the RIDEAU CANAL (1832), Bytown (later OTTAWA) grew to be the largest lumber centre on the river.

Though a few timber barons, such as E.B. EDDY and J.R. BOOTH, made fortunes, many lumbermen and Irish labourers lived in poverty and disease. The ravages of the axe swept up the river and its tributaries. By 1828 there was a sawmill at the future site of PEMBROKE; after 1850 cutting reached the Madawaska River, and by the 1870s Lake Timiskaming. Railways challenged the river by the 1850s, carrying lumber to BROCKVILLE and Ogdensburg, NY. By the 1870s rail lines reached CARLETON PLACE, RENFREW, ALMONTE and Pembroke. Steamers plied the river with goods and passengers, aided by a canal at Carillon, which permitted uninterrupted travel from Montréal to Ottawa. This river transport ceased by 1900.

Most of the valley's stands of pine had been decimated by 1910. Where land was fertile, farmers settled; elsewhere there remained a wasteland of stumps and debris vulnerable to fire. Part of the wilderness was saved from the axe when ALGONQUIN PROVINCIAL PARK was created (1893), and in 1918 Canada's first forestry research station was established at Petawawa to study the effects of logging, disease and fire. With the loss of the larger trees, most mills converted to pulp and paper, still an important industry along the river. But except for the farming area of the lower valley, the heritage of the timber trade is a depressed economy, with little industry and high unemployment. Much of the hydroelectric power gained by harnessing the Ottawa is transmitted to Toronto and elsewhere. Ottawa, which was chosen as Canada's capital in 1857, is clearly the dominant urban centre, but its prosperity is based on the federal government, not on valley resources or its riverine connections. First called the Grand Rivière des Algonquins, the river took its name from a later group of middlemen in the fur trade, the Ottawa.