Susan was the daughter of Benjamin Williams, a native of Roxbury, Massachusetts, who became a prominent Baltimore merchant; and his wife, Sarah Copeland, widow of Nathaniel Morton.

In November 1829, Susan married Jérôme Napoleon Bonaparte-Patterson, the son of Elizabeth Patterson, an American socialite, and Jérôme Bonaparte; their marriage had been annulled after three years on the orders of Napoléon himself so that his brother could make a more advantageous marriage.

[1] Jérôme Napoleon-Patterson, who had graduated from Harvard but found he preferred raising horses to working in law, soon became interested in Susan and the $200,000 fortune she had inherited.

The groom's maternal grandfather, William Patterson, one of the wealthiest men in Maryland, made the financial arrangements for the marriage and gave the couple Montrose Mansion as a wedding gift.

[2] Their wedding was conducted in secret behind the back of his mother, who was away in Europe at the time and hoping for an aristocratic match for her son; Susan and Elizabeth Patterson Bonaparte never successfully reconciled after this rift.