People of Detroit:
The first people to inhabit the Southern Great Lakes region (including the Detroit area) are believed to have been the builders of burial and/or ceremonial mounds (and hence they are referred to as the Mound Builders). The Mound Builders lived in the area before the Native American tribes that we know of today.
Mounds built by these people were of two varieties. One was a conical-shaped earthen mound found to contain skeletons. The other was like a pyramid with the top sliced off. The latter mounds may have been used as lookouts or some sort of communication posts. Large areas of land appeared to have been "marked off" by mounds, as though they were used as a defense system. Other areas contained one large mound surrounded by several small mounds, thus giving way to the theory that they may have been used for ceremonial purposes. The largest mound in the Detroit area was on the eastern bank of the Rouge River and was known as "The Great Mound of the River Rouge". It is said to have been 200 feet long, 300 feet wide and 20 feet tall. When it was destroyed, axes, chisels, pottery, arrow heads, and very old human bones were found inside of it.
The US Bureau of Ethnology estimates that there were 8 distinct groups of "Mound Builders" in what is now the USA. All mounds in southeastern Michigan have long since been flattened and turned into streets and lots.
Links to more Mound Builder information