17. The father of Henry IV and founder of the House of Lancaster, John of Gaunt leveraged his princely birth to become one of the wealthiest men in the world.
John of Gaunt, Duke of Lancaster (b. 1340) was the third adult son of Edward III, King of England. Founder of the House of Lancaster, the descendants of which would claim the throne both before and after the War of the Roses, John spent much of his early life in France and Spain contesting the Hundred Years’ War. Briefly attempting to claim the throne of Castile via his second wife, Constance, John became a leading figure of his father’s government as those around him fell to illness. Becoming a mediating figure during the reign of the young Richard II, John sought to hold the nation together in the face of rebellion.
Due to his princely birth, as well as strategic marriages, John enjoyed significant land grants. Regarded as one of the wealthiest men of his era, John owned land in every county of England as well as reigning as Duke of Aquitaine. Although his lands were confiscated upon his death in 1399 due to the treasons of his son, Henry Bolingbroke, his progeny would return from exile to depose Richard and reclaim the lost possessions as Henry IV. Although difficult to calculate the precise worth of the Lancastrian patriarch, it has been estimated the value of his estate would equate to $110,000,000,000 today.