Classroom Internet Library > Social Studies > American History > Westward Expansion > Primary Sources Classroom Internet Library Primary Sources Northwest Ordinance Online version of the 1787 document that laid the groundwork for westward expansion. Intended Audience: General Reading Level: High School Teacher Section: No Searchable: No The Louisiana Purchase, 1803 Collection of primary source materials dealing with the Louisiana Purchase from the Yale University Avalon Project. Intended Audience: General Reading Level: High School Teacher Section: No Searchable: No Louisiana Purchase Treaty, 1803 Online version of the Louisiana Purchase Treaty with France from the National Archives. Intended Audience: General Reading Level: High School Teacher Section: No Searchable: No Railroad Maps: 1825-1900 Explore the expansion and settlement of the United States with this series of railroad maps from the Library of Congress. Included in the collection are progress report surveys for individual lines, official government surveys, promotional maps, maps showing land grants and rights-of-way, and route guides published by commercial firms. Intended Audience: General Reading Level: Middle School Teacher Section: No Searchable: Yes California as I Saw It This site from the Library of Congress consists of the full texts and illustrations of 190 works documenting the formative era of California's history through eyewitness accounts. Intended Audience: General Reading Level: Middle School Teacher Section: No Searchable: Yes