John Jacob Astor left Madeleine — who gave birth to their son John Jacob Astor VI that August — $100,000 (worth over $2.75 million today), his home on Fifth Avenue, and a $5 million trust fund.

In 1828, John Jacob Astor built a trading post on the Missouri River. Business was so profitable that it only took four decades for Astor to become America's first multimillionaire. National ...