What do we learn about the GM plant's beginnings in Janesville in the nonfiction book, Janesville?

Joseph Albert Craig worked for the Janesville Machine Company, and the company did very well under his management. William C. Durant, General Motors' founder and president offered Craig a job managing a California firm, Samson Tractor. Craig convinced Durant to purchase the Janesville Machine Company, merge it with Samson, and building a new factory in Janesville to house General Motors' Samson Tractor Division.