The Ferguson and St. Louis County police departments had previously been the leading authorities in Ferguson, where protesters have clashed with police since Sunday, resulting in rubber bullets and tear gas being fired into the crowds. The police have also been subjected to gunfire and other attacks, they have said.
"Over the past several days, we've all been deeply troubled by this crisis," Nixon said. "Lately, it's looked a little bit like a war zone and that's unacceptable."
The crisis followed the Saturday police shooting of Michael Brown, 18, an unarmed African-American man.
Nixon said that the operations in Ferguson would be overseen by Capt. Ron Johnson, who Nixon said is from the area. When asked if Ferguson and St. Louis County police would still be involved in patrolling in Ferguson, Nixon said that the effort would rely on a "joint force," but stressed that the highway patrol would be in charge.
"I think we all have been concerned the vision that the world has seen about this region," Nixon said. "We're all about making sure that we allow peaceful and appropriate protests, that we use force only when necessary, that we step back and let the energy be felt in this region."