1. Altitude and configuration of the water-level surface in lower Paleozoic and Precambrian crystalline rocks in the Red Clay Creek Basin, Chester County, Pennsylvania, and New Castle County, Delaware, June through October 1989 and March 1990 Author/Creator: Geological Survey (U.S.), cartographer Publication/Creation: Harrisburg, Pennsylvania : United States Department of the Interior, U.S. Geological Survey, 1991 Resource Type: Map Access & Availability: Loading