Crusaders returning from the East increased European desire for luxury goods from Asia like silk and spices. Marco Polo's travels to China in 1275 further fueled demand. As Europe's population grew and urbanized, demand increased for necessities like salt and luxuries, generating interest in expanding trade. Isabella and Ferdinand's marriage united Spain, allowing them to fund Columbus's 1492 voyage seeking a trade route to Asia that instead landed in the Americas, claiming the land for Spain.