Nixon made the announcement at a news conference Thursday.
Nixon says security will be overseen by Capt. Ron Johnson of the Highway Patrol. Johnson, who is black, said he grew up in the community and "it means a lot to me personally that we break this cycle of violence."
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.
Attorney General Eric Holder said he's concerned that the use of military equipment by Ferguson Police is sending a "conflicting message."
He said the response by law enforcement to protests there "must seek to reduce tensions, not heighten them."
The attorney general said representatives from the Justice Department's Community Relations Service, which works to mediate race disputes, have also been sent to Missouri.
St. Louis Police Chief Sam Dotson says he was so concerned by the way police handled rioting and unrest in Ferguson that he decided to stop sending his city's officers to assist.
Dotson told The Associated Press on Thursday that a 24-officer tactical unit and the city's lone armored vehicle were sent to the St. Louis suburb on Sunday and Monday.
Dotson says he was concerned by how protesters were treated, and for his officers' safety. He decided Tuesday to no longer send officers to the protest area.
Dotson says he isn't being critical, but he would have handled the situation differently.
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