Residents say four different families lived in the units inside the apartment building in the 4800-block of North Lawndale.
The fire broke out around 3 a.m. According to the Chicago Fire Department, the flames started at the back porch and spread quickly.
Residents rushed to get out, and everyone made it out OK. A newborn baby resident named Jayden was in the basement apartment at the time. One man in that apartment explained how his puppy saved them.
"The puppy was barking and going to the doors where we sleep. So, my brother woke up, and he looked out in the window and saw something was orange, and there was a fire. So the puppy was telling us that there was fire," resident Gerardo Velacquez said.
The American Red Cross responded to the scene to assist the displaced families. Some residents were saying they planned to go live with other relatives.
Residents were allowed to go back inside the building to get some of their belongings at approximately 7:30 a.m., but at least one hotspot rekindled. So, fire crews were redeployed to the scene.
The cause of the fire is under investigation.