A tow truck driver called 911 after spotting the woman on South Gessner near Gustine around 11 p.m.
Initial police reports showed that the woman may have been hit by a car, but after authorities found no signs of a crash, investigators were called to the scene.
The woman died at the hospital, and now homicide investigators are working to figure out how she ended up on the road.
Anyone with information is urged to call 911.