Ducksters
Ducksters: Biography for Kids: John D. Rockefeller
Kids learn about the biography of entrepreneur John D. Rockefeller including his early life, building standard oil, business monopoly, fun facts, and charitable giving on this website.
Other
A Classification of American Wealth: America in the Gilded Age
This site's section, which is part of a larger article on the Gilded Age, focuses on the railroad which began to grow in the latter half of the nineteenth century.
Siteseen
Siteseen: American Historama: Bessemer Process
Provides a summary and detailed facts about Henry Bessemer who invents a process in 1855 to create steel from iron.
Wikimedia
Wikipedia: Secondary Source
This brief Wikipedia encyclopedia article explains the difference between primary and secondary sources.