Milwaukee Police are searching for the suspects who tagged garbage cans and buildings, including a public library, with graffiti.
Neighbors first spotted the graffiti Thursday morning near 9th & Mitchell.
Police released images of three male suspects caught on surveillance video around 3:40 a.m.
Investigators said anyone with information about who the three men are should contact MPD District Two.
Sheila Long, who lives in the area, said the markings upset her.
"It's disgusting, because these people are writing on someone else's property," Long said. "We don't even know what these signs mean."
Long said the graffiti also sends a poor message to the neighborhood's youth.
"We've got so many kids out here," she said. "We don't want them to grow up thinking, 'Hey, we can do the same thing these other people, these ignorant people, did.'"
The Historic Mitchell St. Business Improvement District began work to clean up the graffiti immediately, said Executive Director Nancy Bush.
"We arrange for the removal of graffiti as soon as possible after it appear," Bush said.
She said keeping the neighborhood clean encourages shoppers to patronize the businesses there. Bush added it encourages more businesses to buy or rent properties along historic Mitchell Street.
"I hope it sends a message, and continues to, that this business improvement district is cared for," Bush said.
She said some graffiti can be painted over. Other surfaces require that the tagging be washed off with water blasting.
Bush said the BID arranges and carries out the removal, but the City's Department of Neighborhood Services pays for half of it.
She said the Historic Mitchell Street BID typically spends $8-thousand to $10,000 per year on graffiti removal.