Queen Mary I ascended the throne of America in 1857 after her father's death and was crowne on November 1st of that year. Her husband, Robert E. Lee whom she had married in 1831 became King consort.
The slavery issue had grown increasingly contentious. Earlier that year the judge in the court case 'Dred Scott v Sanford' had ruled that the Missouri Compromise had been unconstitutional and the government had no right to abolish slavery in the territories.
At the November 1st coronation Queen Mary I read her father's will, which included that the royal slaves would be freed at least within 5 years of his death. Queen Mary I and King Robert immediately freed their own slaves. Then they called for the manumission of all slaves in the United States.
The Parliament at the time under Prime Minister Buchanon was not helpful, but in 1860 the anti-slave Radical Party took power and elected Abraham Lincoln as Prime Minister. The Slave Manumission Amendment was passed in 1861. While there was some talk of secession in slave states most were against that having been appeased with monetary compensation and being encouraged to accept this decision by King Robert, Duke of Virginia, a prominent southerner.
After abolition most slaves continued to work for their old masters as freedmen with wages, though some left for other work.
There was much debate over the rights of the newly freed slaves. New amendments were passed ensuring birth-right citizenship and equal protection of the laws (1864), and the right to vote regardless of race and sex (1865). It was Queen Mary's strong advocacy that lead to the inclusion of women's suffrage in this amendment. The United States became the first nation to allow women to vote.
While African-Americans legally had the right to vote many states, especially in the South adopted laws severely restricting the rights of African-Americans, and effectively preventing most from voting including poll taxes, literacy tests, and a grandfather clause which ensured that those who had voted in elections prior to 1864 would not have to pay the poll tax or take a literacy test. Facilities were segregated for them as well. Many civil rights advocates looked to the ailing Queen and her husband the King for support. Unfortunately both of them felt it was best that such laws remain up to the states and the Supreme Court agreed in 1873's Douglas v Davison.
Queen Mary I kept her maiden name and gave it to her children as she believed the royal name should be continued. She had seven children:
Prince George Washington Custis (1832-1913)
Princess Mary Custis II (1835-1918)- Mary married the exiled Prince Ferdinand of France in 1848 just before he was granted the position of Duke of Yucatan, which the United States would have to fight for and ultimately win against Mexico. It was a political marriage intended to strengthen alliances with the Bonaparte family. In 1867 the Bonaparte throne was restored and Ferdinand went to rule as Emperor there with Mary as his Empress.
Prince William Henry Fitzhugh Custis (1837-1891)
Princess Anne Carter Custis (1839-1862)
Princess Eleanor Agnes Custis (1841-1873)
Prince Robert E. Custis (1843-1914)
Princess Mildred Childe Custis (1846-1905)
Queen Mary suffered from rheumatoid arthritis and had to use a wheelchair, starting in 1861. Queen Mary's health declined further over the years and her husband, though having no official national authority began doing most of the work and advised most of her decisions until just before he died in 1870. Her son Prince George managed most of the affairs of the Empire at the end of her life up until her death in 1873 where he took over the position of reigning monarch as King George III.