The Euro-American discovery of the ancient city of Aztalan created a stir in 1836. The remains of stockade walls, large flat-topped mounds and what appeared to be ruins of houses impressed early visitors and fired their imaginations. It was not until Samuel Barrett of the Milwaukee Public Museum completed excavations at the site in 1919 that the true nature of Aztalan began to be revealed.

Aztalan's original occupants surrounded their village with a wall made of upright wooden posts covered with a plaster made of clay and grasses, which enclosed 21 acres. They placed watch towers along the wall indicating that it was probably defensive, although it also divided the village from the surrounding fields. Inside the walls, people lived in houses with plaster walls, thatch roofs, and central hearths used for heating and cooking. The inhabitants built four flat-topped ceremonial mounds, each with a structure on the top, within the walls. A priest, or leader, probably lived on one, another house was used as a charnel house, or mausoleum, and still another may have been a place of worship.

Outside the wall, large fields of corn, squash, beans, and other crops were cultivated. The area was rich in game and the residents of Aztalan constructed a fish weir, or fish trap, in the creek adjacent to the site. Aztalan residents were also involved in an elaborate trading network acquiring and distributing items from all over the Midwest.

Native people who moved into Wisconsin from northern Illinois probably established Aztalan to expand their territory and open new areas for trade and possibly settlement. Aztalan was a thriving community for nearly 300 years, but at about AD 1200 the village was abandoned.

The park is open seasonally from May through October.