In St. Louis, Missouri, about a mile west of the majestic Mississippi River, there stands a Civil War–era structure that once presided over Lucas Place—the city’s most elite neighborhood at the time. Today a museum, the austere, painted-brick facade of the Greek-Revival mansion once known as Campbell House is poised gracefully amidst warehouses and office buildings, belying what is contained within—exquisite treasures from a lavish mid-1800s household that once hosted parties and presidents.