Hello Jaema,
Apparently they collected home values from the Philadelphia Department of Records and Board of Revision of Taxes. Since you are in Oakland County, you could aggregate this information from the Register of Deeds office yourself. (They charge you for documents, and all that is recorded is the mortgage amount, which may be less than the homes' values.) An easier and more cost effective option would be to look at Trulia.com and Zillow.com to see estimated values of homes on a map. If your library is friendly with anybody that is a realtor, they could pull real estate comps from the surrounding homes to give you more precise data.
Best of luck,
Steven