I've always thought my particular bit of land verged towards the colder zone. We were listed as zone 5 and I've found anything planted on the west/north/east better be pretty darn hardy to Zone 4. On the south side of the house, we have fences, bushes, trees and lots of winter growth - we can occasionally over-winter an annual or two.
To the right of this blog, you will find a link to the hardiness zone finder. Click on it and enter your zip code.
Remember: Hardiness zones are "guides" not gospel. Most garden spaces have a number of hardiness zones depending on the lay of the land, sun/shade exposure, wind/windbreaks, soil composition, and mulch.