The attack happened Friday around midnight in the area of 53rd and Woodlawn.
Police say the attacker forced the woman into the laundry room of an apartment building, then beat and sexually assaulted her. The offender ran away.
Crime tape still hangs near the laundry room where the woman, believed to be in her late 60s or early 70s, was found by one of her neighbors.
"She was naked from here down, both her eyes black and blue and her mouth and nose...And I assume she was raped," said Mary Cotton, neighbor.
Cotton says the victim did not tell her what happened nor did she want Cotton to call police. But neighbors called anyway.
Another neighbor, Darlene Day, says she heard someone screaming.
"I didn't think anything of it because I hear stuff out there all night, I wasn't thinking about it being the lady," Day said.
Residents say the victim was known to walk outside of her Hyde Park apartment late at night.
"I used to drive up with groceries or something after dark and she would just come out of nowhere and say, 'you better be careful, it is dangerous out here,'" Day said.
The apartment building is owned by the Chicago Housing Authority. While it is designated as a CHA family building, most of the units are occupied by senior citizens.
The small building sits on a well lit corner in an area residents say is patrolled by Chicago police and University of Chicago police.
"I've been here for 10 years. I thought it was safe and everything. It really shook me up," said Cotton.
"When this was happening, the sensor lights kept going off and on, off and on, so whoever did it didn't mind the bright lights," said Day.
The residents ABC7 spoke with have lived in the building for several years and they say there has never been a violent crime in recent years. The CHA calls it a very unusual incident for the area and has already changed the locks to the laundry room and to every unit.
Residents say the victim remains in the hospital and has yet to be interviewed by police.
Anyone with information should call Chicago police.