Not long after he arrived in New York, Pierpont fell in love with Amelia Sturges (called Memie), the daughter of Jonathan Sturges, a well-known merchant and patron of the arts. When Memie and her parents decided to take a grand tour of their own in 1859, Pierpont drew them up an itinerary. He met them in London at the end of their tour, saw Memie every day for the next two weeks, and escorted her family back across the Atlantic.
In the spring of 1860 she agreed to marry him, but early the following winter she came down with a severe cough that did not go away. Refusing to postpone the wedding, they were married on October 7, 1861, and the couple went to the Mediterranean for a honeymoon cure. In Paris lung specialists diagnosed Memie’s illness as tuberculosis. She wrote to her mother: "I wish you could see his loving devoted care of me, he spares nothing for my comfort & improvement." Despite his care, four months after her wedding, in February 1862, Memie died. Pierpont was twenty-four years old.