According to the Associated Press, the woman, whose name was not released, was riding in the vehicle with an unidentified man in Granite City near Mitchell in southwestern Illinois when it became stuck on the tracks.
The two were working to free the ATV when the 118-car train struck at about 8.45pm, prompting both to jump away from the impact.
The woman was transported by helicopter but her condition and medical status was not available Wednesday afternoon.
The man was unhurt.
It appears the train did not receive any damage in the incident and an NS spokeswoman told local media that the incident did not occur at a railroad crossing.
An investigation is underway.
