Book excerpt: For more than a thousand years, from A.D. 500 to 1700, the medieval kingdoms of Ghana, Mali, and Songhay grew rich on the gold, salt, and slave trade that stretched across Africa. Scraping away hundreds of years of ignorance, prejudice, and mythology, award-winnnig authors Patricia and Fredrick McKissack reveal the glory of these forgotten empires while inviting us to share in the inspiring process of historical recovery that is taking place today.