A variety of sources were used for the construction of this webpage;
- USGS - 10/10; a reliable governmental website
- BBC Bitesize - 9/10; a reliable, large, specialised education website
- National Geographic - 8/10; a TV and magazine website specialising in geography and wildlife
- Seatle Pi Newspaper - 5/10; a newspaper website, possibly not as well researched or slightly biased to a political perspective
- Washington State Department of Natural Resources - 10/10; a reliable governmental website, with up to date statistics
- Abblanch Geography - 5/10; a more personal website created by a geography teacher
- The World, David Waugh, 1987 - 7/10; a reliable, researched textbook, but slightly outdated and largely based on secondary evidence