Trans-Alaskan Pipeline

One of the world's greatest civil engineering projects, the construction of a pipeline to carry petroleum (crude oil) 1,285 km/800 mi from northern Alaska to the ice-free port of Valdez. It was completed in 1977 after three years' work and much criticism by ecologists. In 1997 the Pipeline delivered more than 20% of US oil production.

The engineers had to elevate nearly half the pipeline on supports above ground level to avoid thawing the permafrost (permanently frozen ground), which would have caused much environmental damage. They also had to cross 600 rivers and streams and two mountain ranges, and allow for earthquakes.