Terry Cooke had two assists for the Rapids.
Officially, it was a sellout crowd at the 18,000-seat stadium, although there were empty seats amid flurries and below-freezing temperatures.
Luciano Emilio scored in the 80th minute on a sharp pass from Kasali Yinka Casal for DC United.
Ben Olsen had a chance to tie it in stoppage time, but Colorado goalkeeper Bouna Coundoul smothered it for his sixth save of the game.
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