This activity is designed to introduce students to the environmental consequences of industrial and urban development in the late 19th century. Students will learn about the devastating effects of industrial waste on the drinking-water supply of Philadelphia in the late 19th century and about the solutions employed to improve public health. They will use primary sources published by the Philadelphia Water Department and the Philadelphia County Medical Society in 1885. One document, a “Sanitary Survey,” quantifies the pollutants being dumped into the Schuylkill River, and the other, an address made to the County Medical Society, describes pollution’s devastating effects.