"Ferguson will not be defined as a community that was torn apart by violence but will be known as a community that pulled together to overcome it," Nixon said at a news conference.
Crowds have gathered in Ferguson since Saturday's shooting of Michael Brown to protest the 18-year-old's death.
Police defended the use of tear gas and smoke bombs to repel demonstrators after another night of chaos. But the police response has drawn heavy criticism.
Earlier, President Barack Obama appealed for "peace and calm" on the streets.
"I know emotions are raw right now in Ferguson, and there are certainly passionate differences about what has happened," Obama said. "But let's remember that we're all part of one American family. We are united in common values, and that includes the belief in equality under the law, respect for public order and the right to peaceful public protests."
Obama, speaking from the Massachusetts island where he's on a two-week vacation, said there was no excuse for excessive force by police in the aftermath of the shooting. He said he had asked the Justice Department and FBI to investigate the incident.
St. Louis County police spokesman Brian Schellman said officers on Wednesday night tossed tear gas to disperse a large crowd of protesters after some threw Molotov cocktails and rocks at officers. More than 10 people were arrested in Ferguson.
"In talking to these guys, it is scary," Schellman said of officers on the front lines of the protest. "They hear gunshots going off, and they don't know where they're coming from."