The 35th Parallel is an imaginary line of latitude that circles the Earth at 35 degrees north of the equator. It runs across several countries, including the United States, Spain, and Japan. This parallel is significant in geography and climate studies, as it often marks the boundary between different climate zones. In the United States, the 35th Parallel passes through states like California, Arizona, and New Mexico. It is also notable for its historical significance, as it was used in various treaties and discussions regarding land boundaries in the 19th century.