The radar installations were built by Canada and the United States during the Cold War to monitor the continent's northern frontier. The string of 63 stations stretched from Alaska to Baffin Island.
While they haven't been used in a generation, the stations were never removed.
The abandoned sites left a legacy of of debris, broken glass, tumbledown buildings, insulation, old boilers, antennas and rusty barrels. They were not only unsightly, but dangerous — many contain PCBs, heavy metals and solvents.
Treasury Board President Tony Clement was in Yellowknife on Friday to announce that all 21 sites controlled by the military have now been cleaned up. The cleanup cost $575 million over 25 years.
Another 21 sites are the responsibility of Aboriginal Affairs and Northern Development.
The DEW line sites had a major impact on northern society.
The stations, and the southerners who staffed them, were sometimes the first contact Inuit people had with the outside world.