Police received a call shortly after 2:00 Friday morning to report the incident.
Workers at a nearby nightclub said the woman was with two other people who were crossing the street. The car that hit the woman left the scene.
Police are now looking for a gray or silver Pontiac Grand Am or Pontiac Grand Prix. It was reported to have Missouri license plates and may have damage to the front passenger side, a broken headlight and damage to the undercarriage.
Police on patrol were told to check area car washes to see if the driver was attempting to wash away evidence from the car.
There are several nightclubs in the area where the woman was hit just south of Busch stadium. The area is popular with baseball fans before and after Cardinals home games.