The winning play began when Nick DeLeon took the ball down the right side into the corner, where he shook off Crew defender Josh Williams and sent a cross into the box.
Columbus goalkeeper Andy Gruenebaum got a hand on it but the rebound came to Pontius, who put it in for his 10th goal of the season.
The victory enabled fourth-place United 11-7-3 (36 points) to keep pace in the Eastern Conference while Columbus fell to 8-8-4.
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