What is the border line around the edge of a map called?

The term used to describe the border line around the edge of a map is known as the neat line. This line serves a crucial function in cartography as it provides a boundary to the map’s content, helping to visually separate the map elements from any surrounding information that may be displayed, such as legends, scales, or grid lines.

The neat line also plays a role in defining where the cartographic information ends, ensuring that any data presented is contained within a clear and specific area. This helps to maintain the map's aesthetic integrity, while also ensuring that the reader can easily identify the mapped area and assess the information presented without distraction.