Improving home energy efficiency has a huge environmental impact. That's why we most of us started doing this work, after all. (Making homes more comfortable and helping people save money turn out to be a pretty terrific side benefits.)

Still, it's easy to get discouraged. If you do, take a look at the Mother Nature Network's quick look back at the past four decades of America's modern environmental movement. We've come a long way since the first Earth Day on April 22, 1970!