Answer:
Which caused the most conflict between the early settlers in the West and the American Indians was the competition for resources between them.
Step-by-step explanation:
At the end of the 18th century an unprecedented territorial expansion began in the United States, through the acquisition of territories, through purchase, or conquest through war, as well as the forced and violent displacement of indigenous populations. It lasted from 1800 to 1853.
Framed in the Doctrine of the Manifest Destiny, America began to extend its territories towards the Pacific Ocean, entering territories considered ancestral by the native peoples. The main motivation of the United States and its settlers to take these territories was the wealth in different resources they possessed (from gold to agricultural resources). In this way, both civilizations clashed over these territories.