The Dynamo extended its unbeaten streak at BBVA to 26 games and gave United their tenth straight loss in Houston.
The game seesawed back and forth during the first half, which neither team being able to find the goal.
The Dynamo took nine attempts on the goal while DC United took two.
In the second half, the Dyanmo scored both their goals, with a it of help from United.
D.C. United’s James Riley went up to block the shot and inadvertently headed the ball into his own goal past goalkeeper Bill Hamid.
Clark got another chance to score in the 89th minute and this time found the goal from the right side of the field.
Houston will return to the pitch on Tuesday evening as they face Santa Laguna at BBVA Compass Stadium in their CONCACAF Champions’ League quarterfinal match.
Kickoff is set for 7 p.m. in Houston.