Final answer:
The Crusades had a significant effect on history by reviving trade between the East and the West, resulting in economic growth and cross-cultural exchanges.
Step-by-step explanation:
The important effect that the Crusades had on history was the revival of trade between the East and the West. As Catholic Crusaders returned from the Middle East, they brought back new goods and knowledge from lands they had never experienced before. This resulted in the expansion of trade and exploration, creating opportunities for economic growth and cross-cultural exchanges.