Peter S. Onuf 
Statehood and Union [PDF ebook] 
A History of the Northwest Ordinance

This new edition of Statehood and Union: A History of the Northwest Ordinance, originally published in 1987, is an authoritative account of the origins and early history of American policy for territorial government, land distribution, and the admission of new states in the Old Northwest. In a new preface, Peter S. Onuf reviews important new work on the progress of colonization and territorial expansion in the rising American empire.