Ropapa Mensah started the scoring for the Hounds in the 16th minute, and Robbie Mertz added another in the 40th minute to give the Hounds a two-goal lead.
Kyle Greig cut the deficit to one for Saint Louis in first-half stoppage time, and Wal Fall scored the match’s final goal in the 57th minute.
The tie gives the Hounds a one-point lead over Hartford Athletic in Group F.
The two teams failed to record a shot in the opening 15 minutes of play.
The Hounds were on the attack in the 16th minute, after Mertz sent a pass to Steevan Dos Santos in the right side of the penalty area.
Dos Santos then sent a cross into the six-yard box, which deflected off a nearby defender and the crossbar.
Man of the match Mensah then kicked the ball over the line, giving the Hounds a one-goal lead.
Another chance came in the 40th minute, when Mertz regained possession in the left side of the penalty area after a deflection. The Pittsburgh native then sent a shot past Saint Louis goalkeeper Kyle Morton into the bottom-right corner to give the Hounds a 2-0 advantage.
Saint Louis’ best chance of the half came in the 45’+1, after Sam Fink sent a long pass to Greig in the six-yard box. The ensuing shot was saved by Tomas Gomez, but Greig was able to send the rebound into the bottom-left corner, making it 2-1.
After winning a free kick in the 57th minute, Saint Louis had a chance to even the game. Fall took the free kick for Saint Louis and sent a right-footed shot into the top-left corner, tying the game at 2-2.