The Ninety-First Meridian is a line of longitude located at 91 degrees west of the Prime Meridian. It runs from the North Pole to the South Pole, passing through several regions in the United States, including parts of Arkansas, Mississippi, and Louisiana. This meridian is significant for geographical and navigational purposes, helping to define time zones and map coordinates. In addition to its geographical importance, the Ninety-First Meridian also serves as a reference point for various studies, including climate and ecology. Researchers often use meridians like this one to analyze patterns in weather, vegetation, and human activity across different regions.