http://memory.loc.gov/ammem/collections/jefferson_papers/

Use the light blue search box on the left and enter “Louisiana” to find the relevant documents from this collection.

http://memory.loc.gov/ammem/collections/madison_papers/

The search function can be used in both these collections to find correspondence with participants in the Louisiana Purchase such as Robert Livingston, William C. C. Claiborne, and James Wilkinson.

http://memory.loc.gov/ammem/collections/maps/lapurchase/

This special collection of documents, maps, artifacts and newspaper accounts is from special and general collections in the Library of Congress

http://www.loc.gov/rr/program/bib/presidents/monroe/index.html

A guide to materials on James Monroe available at the Library of Congress and elsewhere.

Includes excerpts from the Annals of Congress covering the debates over the Louisiana Purchase. On the issue of free navigation of the Mississippi River, see the debates and votes for resolutions (February 25, 1803) authorizing the President  to  “organize, arm, and equip, according to law, and hold in readiness to march, at a moments warning, 80,000 effective militia.”

http://memory.loc.gov/ammem/amlaw/louisianapurchase.html

http://www.thnoc.org/

http://www.monticello.org/site/research-and-collections/research-tools

This website includes resources relating to Jefferson.

Article on the Louisiana Purchase, including additional documents and bibliographical references:  http://www.monticello.org/site/jefferson/louisiana-purchase

Biographical information on James Monroe: http://www.monticello.org/site/research-and-collections/james-monroe

http://www.mcu.es/archivos/MC/AGI/FondosDocumentales.html

http://www.archivesnationales.culture.gouv.fr/anom/fr/

http://cls.louisiana.edu/

Copies of several reports, maps, documents and letters in Spanish and French are also available at the Center for Louisiana Studies, Lafayette, Louisiana.

http://www.crt.state.la.us/louisiana-state-museum/index