Lethbridge, Alta, City, pop 74 637 (2006c), 67 374 (2001c), inc 1906. Lethbridge is located 215 km by road southeast of CALGARY overlooking the steep, coulee-dissected valley of the OLDMAN RIVER.

Nomadic BLACKFOOT claimed the Lethbridge area as their summer hunting territory prior to European contact. Significant European incursions did not begin until 1869 when Montana traders built FORT WHOOP-UP. It was among the most notorious of the whisky-trading posts that spread across the Prairie West.

Large-scale coal mining became feasible in 1885 when the North Western Coal and Navigation Co, directed by Sir Alexander GALT and his son Elliott, completed a railway to their mine from Dunmore on the CANADIAN PACIFIC RAILWAY (CPR). The population of the mining camp jumped from 4 in 1881 to 2353 in 1891 as a townsite emerged to serve the fast-growing colliery workforce. Named Lethbridge in 1884 after North Western Coal's first president, William Lethbridge, the town was incorporated in 1890.

A second rail link leading to the Montana border was completed in 1890. The CPR began to operate the Lethbridge-Dunmore line in 1897 and extended it west to coal mines in the CROWSNEST PASS. Lethbridge became a CPR divisional point in 1905 and was soon incorporated as a city. In 1909 the CPR completed an impressive single-track viaduct across the Oldman River Valley. Just over 1.6 km long and 96 m above the valley floor, it is reputedly the longest and highest bridge of its type in the world and Lethbridge's most dramatic landmark. Railway investments made Lethbridge the principal marketing and distribution centre between Calgary and the US border.

Irrigation played a major role in the evolution of Lethbridge as agriculture gradually displaced coal as the key local resource. Between 1898 and 1900 Mormon migrants from Utah built a 185-km system of canals to divert the St Mary River, the first large-scale irrigation system in Western Canada. The land area supplied with irrigation water expanded between the World Wars and doubled from 1965 to 1985.