[1] After a 14-day overland trip to Le Havre, followed by a 62-day ocean voyage aboard the ship Marengo, the family arrived in New Orleans, Louisiana, on Christmas Day 1835, then traveled up the Mississippi River to St. Louis, Missouri, finally settling on a farm in Belleville, Illinois.

[5] During an epidemic of malaria that killed his eldest sister, Eugene was stricken as well, and the resultant fevers and impaired eyesight plagued him for the next several years of his young adulthood.

He educated himself in the fields of botany, chemistry, and physics, but his continued precarious health led doctors to suggest a change in climate, so in 1848 he traveled to Washington, D.C., with his eldest brother Julius, who was returning to his job at the United States Coast Survey.

[7] Eugene spent four months in Washington, meeting through his brother such noted scientists as Joseph Henry, Spencer Fullerton Baird, and Alexander Dallas Bache.

That fall he went to Philadelphia to attend a variety of lectures, and during a visit to the laboratory of James Curtis Booth at the Franklin Institute, it was suggested that he return to Germany to study analytical chemistry.

During a summer trip with his brother Theodore to their native province, the turbulence of the Palatinate-Baden rebellion forced the pair to seek safety in Speyer, where their cousin was a government official.

Hilgard spent three semesters at Zurich, studying under notable professors such as Lorenz Oken, Arnold Escher von der Linth, and Carl Jacob Löwig, the latter of whom appointed him as his laboratory and teaching assistant.

Despite a productive period of study under Karl Friedrich Plattner, a recurrence of his health problems, combined with two near-death experiences involving cyanide gas and mercury vapor, led him to conclude he was not cut out for the hazardous world of mining and smelting.