Use this link to the Search for Success Database of Online Resources.
The encyclopedias: World Book Student, Britannica Online School Edition, Multimedia Encyclopedia (Groliers) and America the Beautiful (Scholastic) may be useful.
Also look for the US History in Context Database and use the results labeled 'reference' .
Remember all the wphl online resources require a password. If you access the site from home, the user ID is: highlandsms.