Workers, suspended by ropes, drill into a wall during the construction of the Grand Coulee Dam, Washington, USA. Work to originally build the dam began in 1933 and was completed in 1941. The dam is one of the largest concrete structures in the world at 168 metres high and 1,272 metres long, with a thickness of 152 metres. 78 people died on the original construction of the dam. The dam is currently the largest hydroproducer in the United States.