The 36th Parallel North is a circle of latitude that is 36 degrees north of the Earth's equatorial plane. It runs across several countries, including parts of the United States, Spain, and Japan. This parallel is significant in geography and is often used as a reference point for various studies, including climate and agriculture. In the United States, the 36th Parallel North is notable for its historical context, as it served as a boundary in the debate over the expansion of slavery before the Civil War. It also crosses through regions like California, Arizona, and New Mexico, influencing the climate and ecosystems found in these areas.