Caroline Slidell Perry was the daughter of Jane Slidell and Matthew Perry, commodore of the U.S. Navy during the Mexican-American War and the War of 1812. Her father also played a leading role at the Convention of Kanagawa, which opened Japan to the West and helped develop the curriculum at the Naval Academy in Annapolis.

In 1849, Caroline married August Belmont, a German Jewish immigrant who managed to work his way up from rather humble beginnings in the Rhenish Palatinate village of Alzey, through an escalating series of positions with Rothschilds, before coming to New York in 1837 to serve as their agent. When the Rothschilds sustained major losses during the Panic of 1837, Belmont established his own financial firm, August Belmont & Company, and accrued a fortune over the next decades. Naturalized in 1844, the following year, a New York newspaper estimated his wealth at $100,000. When August married Caroline, whom he called “beautiful and well-bred,” on November 7, 1849, it was widely regarded as the most fashionable wedding that year in New York.

Beginning in 1852, August undertook a political apprenticeship to Caroline’s uncle, Louisiana congressman John Slidell. He would be deeply engaged in national politics for the rest of his life, later serving for years as the chairman of the Democratic National Committee. In 1853, Franklin Pierce named him to a diplomatic post in Holland. Caroline was rather miserable the whole time, complaining that the Hague was boring, lacked the comforts of New York, and that the weather was too severe.

Caroline and August had six children. They lived an opulent life in New York City, with a country house in upper Manhattan, a farm on Long Island, and a mansion at Fifth Avenue and Eighteenth Street, where they entertained frequently, hosting masquerades, elegant dinners, and private performances.