Price per square foot varies by location, condition and year built. Do you want an average or specific locations? The National Association of Realtors has a report that is much more reliable than Zillow or Trulia. A Realtor can give you a report in a few minutes. Let me know what you need and I'll email it to you.
Zillow has some information available on price per square foot basis. Here is a link. If you contact a local real estate agent with access to the MLS they could run a report for you on the specific types of properties you are interested in.