"The Story of Mankind" tells how people have lived and what things people have done that made a big change in the world. It starts with cave men. It tells about many different people. The last people it tells about are the people that lived when Hendrik Willem van Loon was writing the book. That was just after World War I. At that time, lots of people wanted to make it so that there would never be another war. Hendrik Willem van Loon thought that if he taught children about history, they would not want to fight wars when they grew up.