The United States Geological Survey has been creating maps since 1884, and they're all available online for free.
Free aerial photos and topographic maps can reveal a lot about your property, and a simple hike can turn into a natural history lesson when you can read the woods.
You can see a lot from your trails, but sometimes the best places are stumbled upon by accident. Get off the beaten path and explore your woodlot with the help of a map, compass, GPS unit, or smart phone.