Final answer:
The code that slaves used to navigate northward was part of the Underground Railroad, using not written but visual and audible clues. In contrast to their quest for freedom, southern states enacted Black Codes post-Civil War, which sought to control and exploit African Americans in ways similar to slavery.
Step-by-step explanation:
The code that slaves used to follow as they made their way north was part of the Underground Railroad. This network was designed to assist enslaved African Americans in their escape to free states and Canada. To reduce the risk of infiltration and because many slaves could not read, visual and audible clues such as quilt patterns, song lyrics, and star positions were used for navigation.
In contrast to this network of freedom, after the Civil War, southern states enacted Black Codes, restrictive laws that sought to control the African American population and maintain a cheap labor force similar to slavery. These were based on the pre-emancipation Slave Codes, and despite granting some legal rights, they imposed numerous restrictions, including prohibitions on bearing arms or testifying against whites.