The protest was the latest of several since a judge on Friday announced a not-guilty verdict for a white former St. Louis police officer charged in the shooting death of a black suspect. The gathering had been designed to show white support for the protesters' cause.
Demonstrators marched down a busy street to Busch Stadium about an hour before singer Billy Joel was scheduled to perform in front of an estimated 50,000 fans. Metal barriers had been set up around the baseball stadium, and the marchers stood outside the venue chanting.
There was a brief skirmish when it appeared some protesters attempted to get through the barriers.
Marcher Jennifer Sherer of St. Louis said the city remains badly segregated and historically the racial divide has been intentional.