Police were called to a home on 18th Street around 6 p.m. Wednesday night after the woman's son found her.
When police arrived they found the body of 82-year old Geraldine Urness. Police say she suffered an apparent head wound. The woman's car was missing.
Rockford's police deputy Chief Dominic Iasparro said a suspect was taken into custody shortly after 9 p.m. The suspect was picked up at an East Side fast food restaurant.
No formal charges have been filed, but police have been questioning the suspect all day.