This document summarizes the key factors that led to westward expansion in the United States during the early 1800s. It discusses geographic, economic, and overland trail factors that motivated migration. It also outlines how population growth, cheap western farmland, and new transportation routes like rivers, canals, and the recently invented steamboat facilitated westward movement of settlers seeking new opportunities. Major overland trails like the Oregon and Santa Fe trails are noted, along with dangers of travel. The document also briefly discusses the California Gold Rush of 1849 as another driver of expansion.