Landon Donovan scored the only goal of the game as the Galaxy became the first MLS side to mathematically qualify for the postseason.
Paolo Cardozo had two chances early on to put the Galaxy ahead before LA broke through. Sean Franklin shifted the ball over to Landon Donovan with the Rapids defense in disarray and the LA captain slotted a shot past Matt Pickens.
Colorado did put the ball past Donovan Ricketts, making his first appearance since an arm injury suffered against the San Jose Earthquakes on June 25, in the second half, but Wells Thompson was whistled for offside.
With the win Los Angeles remains the only MLS side to remain undefeated at home in 2011.