Final answer:
The last name of the person described is Gould. He was involved in various industries and has a city named after him.
Step-by-step explanation:
The last name of the individual described in the question is Gould. His first name is mentioned as William.
William Gould was a prominent figure in the late 19th century, known for his involvement in various industries, including as the director of the Northern Pacific Railway, the founder of American Express, and as a co-founder of a company that still bears his name today. He also has a city named after him with a population of 120,000.