Maryland Department of Natural Resources

Educational Publications

A Geologic Walking Tour of Building Stones of Downtown Baltimore, Maryland

2001, Sherry McCann-Murray

Educational Series 10


A great variety and quality of native building stones used in Baltimore come from the geologic part of Maryland known as the Piedmont Plateau Province (Map 1). Roughly the western half of the City of Baltimore lies in the Piedmont Plateau Province. Ranging in age from about 200 million to 1.1 billion years old, Piedmont rocks consist of granite, gneiss (pronounced “nice”), slate, marble, quartzite, and other rocks. Most of these rocks are igneous or metamorphic in origin, but a few rocks have a sedimentary source. The majority are hard, durable, attractive, and polish well, making good building stones.

Although some of the building stones observed on this tour were extracted from quarries in Maryland, most of the stones are not native to Maryland. An assortment of rock types was selected for this tour of downtown Baltimore, however, there are many more types of building stones located around the city which can be explored.

The route was selected to illustrate a variety of building stones in a small geographic area near downtown hotels. Some additional examples of the building stones that are described in this booklet, are present in buildings along the route between Stops, but are not specifically mentioned in the text for sake of brevity. After a while, the observer will be able to recognize some of the more common building stones (e.g., Indiana Limestone). The complete tour should take less than two hours, but you can tailor it to your needs.