Schoonmaker Reef

Schoonmaker Reef is a fossilized coral reef in the Menomonee River valley made up of dolomite rock from the Silurian period. This rock outcrop displays the preserved remains of marine organisms that accumulated in an ancient shallow sea.

The formation was discovered in 1844 and identified in 1862 as the first ancient reef found in North America. From 1838 to 1909, the site served as a quarry and lime production facility before its full scientific importance became recognized.

This site reveals traces of an ancient coral reef that holds fossils and draws visitors into the story of an old ocean. The location connects people today to a time when this region was covered by water, visible through the rocks beneath their feet.

The reef lies in northern Wauwatosa between two streets, making it relatively accessible to reach. Visitors should know this is a protected site surrounded by nearby roads and residential areas.

The Schoonmaker family gave the reef its name after operating it as a lime kiln between 1838 and 1909. This practical use of the site shows how people extracted value from the geology for local needs.