Go to the U.S. Geological Survey Store (don't let "store" turn you off - downloading USGS maps is absolutely free). Scroll down about half way and click "Maps Locator". Follow the ques from there to download a free, large-scale map of your choosing from anywhere in the US. Once you've downloaded the large PDF file, take it to a large-format printer's (even Kinko's can do this) and have it printed. Or, do it yourself on a small-format home inkjet printer and piece it together for a lower budget and different look.