PBS
Pbs Online News Hour: Green Party History
PBS Online provides this profile of the Green Party in the United States and other nations.
Wikimedia
Wikipedia: Whig Party (United States)
Wikipedia offers detailed information on the United States Whig Party. Includes info on the creation, growth and end of the Whig Party.
Wikimedia
Wikipedia: Green Party of the United States
This site from the encyclopedia Wikipedia provides an overview and history of the Green Party of the United States. Gives a definition and a good historical description.