Philadelphia Inquirer (1981-present) Try searching for Walmart AND [name of location] for sites around the Philadelphia area
Philadelphia Daily News Try searching for Walmart AND [name of location] for sites around the Philadelphia area
Proquest Newsstand Find papers from other states and cities here.
Philadelphia neighborhoodBase Searchable database of data and descriptions of Philadelphia neighborhoods from the University of Pennsylvania's Cartographic Modeling Lab
ZIP Code Statistics U.S. Census Bureau statistics
SimplyMap can be a little tricky to use, but you can create detailed reports on a surrounding location or zip code. It requires registration with your Temple email address to identify you with Temple.
You can find a number of "free" web sites with zip code demographics. Usually, they don't tell you the source or age of their data, which makes them useless as a reputable source, but they can give you ideas about what to look for in the sources above. For example, City-data.com and MyBestSegments
Academic Search Premier is a database that links you to articles from national and scholarly sources that address issues more generally. A link here is to a search for the company name Wal-mart to which you can either narrow to a publication type (try Academic) or add words to make the search more specific. You can also use this for general articles on food production and ingredients. For example, Wal-mart AND employ*.
See also the review article WalMart and Local Economic Development: A Survey.