Ancient cultures had ways to remember; in Canaan/Israel they did this with standing stones. If one of their “gods” (or so they believed) caused an important event or provided a significant benefit, a stone was erected as a testimony to the action of the “god.” If a covenant or treaty was signed between cities or individuals, stones were erected to declare the agreement and call the “gods” to witness. Travelers who saw the stones would ask, “what happened here?” and the people who knew the story would give testimony to their “gods.” As Israel entered the land of Canaan and  onquered it, God called them to commemorate certain of His actions in a way the culture understood: standing stones.
Scripture: Joshua