The three maps in these cases and the large wall map above them cover almost 100 years of the early mapping of America. From 1733 to 1814 they show the growth of cartographic knowledge based on surveys, explorations, and travel accounts. Pownall’s 1776 map shows the kind of detailed mapping that filled in the broad regions depicted in Popple’s 1733 wall map. Humboldt’s 1811 map details the American southwest and Mexico, areas only generally covered in early mapping. Finally, the Lewis and Clark map of 1814 provides on the ground discoveries from their own journey to the Pacific, all of which are shown in their map and were later used by the best cartographers in their maps of America. These four maps illustrate well the way maps improve over time and draw on each other to provide an increasingly accurate picture of the world.