Figure 1.--Geology of the United States as represented by Maclure (1817). Original map in color. Note: To facilitate comparison of figures 1 through 4, the original geological representations have been replotted on the same projection and base. State and national boundaries are retained as they existed at the times of publication; in figures 3 and 4 the geography west of the Mississippi River and within the coastlines is retained as on the originals.