According to the quotes by black hawk and massasoit ousamequin, which was the malor source of conflict between american indians and u. s. citizens during the early 1800s

Answer is: ownership of land.

Black Hawk said in 1882: " My reason teaches me that land cannot be sold. The Great Spirit gave it to his children to live upon. So long as they occupy and cultivate it, they have a right to the soil. Nothing can be sold but such things as can be carried away".