Andrew Carnegie grew up poor in a one-room cottage but became a steel tycoon, donating millions to educational causes. Samuel Walton milked cows and delivered newspapers as a boy but founded Walmart, becoming the richest man in the US. Oprah Winfrey experienced hardship and abuse as a child but became the richest African American of the 20th century and wealthiest self-made woman in America. These stories profile seven entrepreneurs who rose from humble beginnings to achieve great success.