If it is indeed Lincoln, it would be the only known photo of the 16th president in front of the executive mansion and a rare find, as only about 130 photos of him are known to exist. A copy of the image was provided to The Associated Press.
Grant's 38-year-old great-great-grandson, Ulysses S. Grant VI, had seen the picture before, but didn't examine it closely until late January. A tall figure in the distance caught his eye, although the man's facial features are obscured.
The AP story did not go into the details of exactly "when" the photo was taken or "why" it might be considered the last photo prior to the assassination.