The robbery and sexual assault happened in the 2600-block of N. Wilton at about 2:30 p.m.
Police say the attacker fled the area immediately afterward. They are not able to provide a description of the attacker.
Lots of neighbors were out walking on a warm evening, but few had heard about the attack inside an apartment on their block. People in the neighborhood say they are alarmed.
"It's very scary. This is supposed to be a safe neighborhood and I've always felt safe, and it's really scary," said a resident of the neighborhood named Robin.
Police say the woman was robbed at gunpoint and then sexually assaulted inside her apartment.
The neighborhood is not far from DePaul University and is home to a number of college students.
"We thought this neighborhood was safe. It supposedly has been safe. It is one of the better neighborhoods in Chicago," said neighborhood resident Jimmy Woolert. "To have something like this to happen here, it's very unnerving, very shocking."
Details on the crime inside the neighborhood are scarce. Some neighbors say they have seen an increase in suspicious activity recently - nothing, however, like this.
"You could just be at home. I mean, that someone would somehow force themselves in - it's really scary. I really, really hope they catch the person," said Robin.
The victim was treated at a local hospital. ABC7 had not been able to learn anything about her condition as of Wednesday night. Police tell us they have no suspects.