North America's natives have often been conquered and displaced with the progress of European colonization in the territories of the contemporary United States.

The native population had declined after Europeans arrived, and for various reasons, primarily diseases such as smallpox and measles.

Violence is not a significant factor in the overall decline among Native Americans, though conflict among themselves and with Europeans affects specific tribes and various colonial settlements.

In the early days of colonization, many European settlers were subject to food shortages, disease, and attacks from Native Americans.

Native Americans were also often at war with neighboring tribes and allied with Europeans in their colonial wars.

At the same time, however, many natives and settlers have come to depend on each other.

Settlers trade for food and animal pelts, natives for guns, ammunition and other European wares.

Natives have taught many settlers where, when and how to cultivate corn, beans and squash.

European missionaries and others feel it is important to "civilize" the Native Americans and urge them to adopt European agricultural techniques and lifestyles.