The Antebellum Economy, Are these sources credible?

http://eh.net/encyclopedia/article/wahl.slavery.us%20This This site seems highly credible due to the large amounts of references and it's logical view point. The site is also owned by the Economic History Association. It was also written by Jenny B. Wahl of Carleton College. The site also provides substantial information and detailed charts to provide support for the information. Robert Whaples is the editor of the site and his name is displayed directly on the web page.

http://www.history.iastate.edu/agprimer/Page28.html This site is fairly credible because it is from Iowa State University but it was posted by Knut Oyangen who may not be credible due to a lack of title. One may also contact the web master but this doesn't say when this information was posted. This site also has many references and is quite logical.