Nadirah Al-Kaabah, 35, admitted to beating the child, Nyeem Kitchen, with objects inside the bedroom, according to police.
Al-Kaabah also has 16 prior arrests, including for aggravated assault, police said.
When officers arrived they discovered the baby boy unresponsive with obvious head and neck bruising, police said.
He was pronounced dead at the scene.
A neighbor who lives next door to the home told ABC over the weekend he heard someone screaming on the front porch of the house.
"I was upstairs in my room, and I heard her sister screaming, crying outside, 'oh my God the baby's dead, the baby's dead,'" said Abdul Saleem Aziz.
Surveillance video from a convenience store across the street captured the initial moments police and medics arrived on the scene. The video also showed the mother being escorted out of the home by Philadelphia police.
Aziz said the sister of the boy's mother told him she was communicating with her sister Friday night.
She said the mother was telling her there was something wrong with her child, and when she showed up to the home Saturday morning, Aziz said the sister found the baby unresponsive.
"She went upstairs to get the child, and she said when she looked at the baby it was like cold and blue, and she said she just ran out the room screaming," said Aziz.
Aziz and other neighbors said the mother had lived in the boarding home alone with her baby for about two months, and kept to herself.
"She used to have him strapped to her chest like a carrier, you used to see them come and go, they don't ever say nothing," said Aziz.
Neighbors said they were heartbroken to find out the infant had passed away so soon.
"That's heartbreaking, I have three children of my own, so I'm just here thinking like if I was to come home, or wake up and find one of my children was deceased in the house," said Isaiah Johnson, a neighbor.