If you've spent a decent amount of time in National or State parks in the U.S., you've probably been in a building built by a federal program that employed nearly 3 million people during the most difficult economic time in our country's history. Their work constructed trails and shelters in more than 800 state and national parks. They built wildlife refuges, fisheries, water storage basins and animal shelters. They built bridges and campground facilities, many of which are still in use today.

Today on America's National Parks, the Civilian Conservation Corps.