The term 'span of history' refers to the length of time that a particular event or period has been in existence. The crossword solution for this term is ERA, which stands for Epoch, or a period of time in history. An ERA is typically divided into smaller periods of time, such as centuries or decades, and can be used to refer to any period of time in history. It is often used to refer to a specific period of time, such as the Middle Ages or the Industrial Revolution.