Remains of Ice Age settlements dating back more than 10,000 years have been found in Pennsylvania. Little is known of the peoples who lived there except that they were nomadic hunters who had migrated from the west. It is believed that later Indian tribes who occupied the region prior to historic times were also nomadic.

When European explorers arrived in the 17th century, the Indian population of the area was about 15,000 to 20,000. Indians of the Algonquian language family lived in eastern and central Pennsylvania. In the east were Indians who called themselves Lenni-Lenape ("Original People"), but were named Delaware by the English. The Shawnee Indians occupied central Pennsylvania. In western Pennsylvania were tribes of the Iroquoian language family.