In the early 1800's, Saratoga Springs was known as a health resort because of its world famous mineral springs. The springs in the city are unique because they are highly mineralized, highly carbonated cold water springs. Beneath the city, rock layers of limestone and dolomite were formed in ancient tropical oceans, and millions of years ago earthquakes fractured the layers that hold the mineral waters, creating a normal geologic fault that allowed the highly charged water to bubble to the surface in a few places. These early springs were used by the Mohawk and by early settlers. Later, technology allowed more mineral springs to be drilled to meet the demand of summer visitors. The fault responsible for the springs can be clearly seen in High Rock Park, and streets going east from Broadway, including Lake, Caroline, Phila and Spring Street, descend the face of the fault. In 2015, the city re-drilled the High Rock Spring, adding another spring for use. High Rock Spring was the first mineral spring visited by the Mohawk, Congress Spring in Congress Park became famous through the efforts of Gideon Putnam and John Clarke, by 1900 the city had about 200 mineral springs in operation, excessive drilling depleted the water table, and state legislation in 1908 limited the number of springs to 17 to protect the resource.