https://www.nps.gov/nr/travel/lewisandclark/journey.htm
https://www.nps.gov/nr/travel/lewisandclark/gre.htm
https://www.history.com/topics/westward-expansion/lewis-and-clark
https://www.monticello.org/site/jefferson/lewis-and-clark-expedition-journey-west
http://www.americaslibrary.gov/aa/lewisandclark/aa_lewisandclark_bears_1.html