This year's park week will follow the theme "Healthy Parks, Healthy People" and explore the connection between human and environmental health and the role America's parks play in both. It also helps that the week coincides with Earth Day, which is April 22.
In addition to the fee-free days, the parks will offer special National Park Week activities. North Carolina's Congaree National Park will throw NatureFest 2011 on April 16 and 17 and lead nature walks and canoe tours as part of the free fun. At Pennsylvania's Steamtown National Historic Site, you can board a historic or vintage steam locomotive for a short train ride starting April 17.