The Mason-Dixon Line is a boundary that was originally established in the 1760s to resolve a land dispute between the colonies of Maryland and Pennsylvania. It was surveyed by Charles Mason and Jeremiah Dixon, and it later became known as a cultural divide between the Northern and Southern states in the United States, particularly during the Civil War era. This line is often associated with the issues of slavery and states' rights, as it marked the transition between free states and slave states. Today, the Mason-Dixon Line is commonly referenced in discussions about regional differences in the U.S., particularly in terms of culture and history.