Published in 1917, King Coal is a fictionalized account of the coal mining industry in the United States. The book explores the dangerous working conditions, low wages, and oppressive practices faced by coal miners during that time. The book is based on the 1913-1914 Colorado coal strikes and written just after the Ludlow massacre.

Upton Sinclair (1878-1968) was an American writer and social reformer who gained prominence in the early 20th century. He is best known for his novel "The Jungle," which exposed the harsh conditions and exploitation of workers in the meatpacking industry. However, Upton Sinclair also wrote extensively on various other social and political issues.