This document provides an overview of key events and developments during Period 4 (1800-1848) of AP US History. It summarizes the Jeffersonian Revolution of 1800 and Jefferson's presidency. It also discusses John Marshall and key Supreme Court cases, the Louisiana Purchase and Lewis and Clark expedition, the War of 1812 and aftermath, nationalism shaping foreign policy, the Industrial Revolution and rise of factories, internal improvements like canals and railroads, and the development of distinct economic systems in the North and South relating to slavery and cotton.