Susan May Williams (April 2, 1812-September 15, 1881) was the daughter of Benjamin Williams, a prominent Baltimore merchant originally from Roxbury, Massachusetts, and his wife, Sarah Copeland, widow of Nathaniel Morton. In response to the opening of the Erie Canal, which was in direct competition with the port of Baltimore, Benjamin Williams became one of the founders of the first railroad company in the United States, the Baltimore and Ohio Railroad, chartered on April 24, 1827.
In November 1829 Susan married Jérôme Napoleon Bonaparte (1805–1870), Napoleon's nephew, son of the King of Westphalia. He had refused to wait for an arranged marriage to a European princess, opting instead for the promise of the $200,000 fortune she brought to the marriage. The groom's maternal grandfather, William Patterson, one of the wealthiest men in Maryland, gave the couple a mansion (now Montrose Mansion) as a wedding gift in an attempt to match the bride's dower.
Their children were Charles Joseph Bonaparte, United States Attorney General and Secretary of the Navy, and Jerome Napoleon Bonaparte II, who served as an officer in the armies of both the United States and France.