Niece of lifelong bachelor and President of the United States James Buchanan who acted as First Lady from 1857 to 1861. She was known for the large collection of European art that she had acquired over the years and donated to the government after her death.
After the death of her father at age eleven, she requested James Buchanan as her legal guardian.
She had three cutters (vessels) named in her honor by the United States Coast Guard.
She was thirty-six years old when she married Henry Elliott Johnston, a Baltimore banker.
She used her time and influence as James Buchanan's First Lady to improve the living conditions of Native Americans in reservations.