Ulysses S. Grant's military fame came later during the Civil War when, in 1864, following a bloody campaign south, he crossed the James River and laid siege to the vital railroad center of Petersburg . The siege lasted nine months and was the longest military operation of the War. Seven miles to the north, Grant established headquarters at City Point - now Hopewell - on a bluff overlooking the confluence of the James and Appomattox Rivers , where this black locust tree stands. Lincoln visited Grant there in June 1864 and reviewed the Union troops .