Map: The Kansas-Nebraska Act of 1854 – Library of Congress – McConnell Map Co. (1919)
The Kansas-Nebraska Act was the seed of division over the subject of slavery in the United States. Congress began to wrestle with the laws of slavery in newly opened territories with Missouri, Kansas and Nebraska caught in the middle. This is a great video on the history of the Kansas-Nebraska Act of 1854 and the beginning of Nebraska Territory from the History Channel (about 3 minutes).
Additional Resources:
Kansas-Nebraska Act: Primary Documents in American History – Library of Congress
Kansas-Nebraska Act – Kansapedia – Kansas State Historical Society
Kansas-Nebraska Act – U. S. Senate