All across the country, national parks are doing their part to make environmentally friendly updates. Here are 10 parks in the U.S. taking steps to be the greenest spaces in America.

Discovery Green Park

Discovery Green Park is the greenest place to be in downtown Houston. It features more than 12 acres of green lawns, dog runs, lakes, eco-friendly art displays and playgrounds. The buildings in Discovery Green Park were built using sustainable methods and sport LED light bulbs and solar power. Park managers use organic gardening and landscaping methods to keep the grounds looking pristine and use recycled groundwater to keep plants and trees from getting too parched. Oh, did we mention the on-site recycling center?

Washington Park

Washington Park in Portland, Ore., is green by default. After all, Portland was named one of the most eco-friendly cities in the country. With more than 400 acres of wildlife, trails and recycled art, this park won't disappoint.

Astoria Park

Astoria Park in Queens, N.Y., is known for its beauty among otherwise urban landscapes, and will switch its park utility vehicles over to green alternatives within the next year. These cars will be small, energy efficient hybrids that won't make any carbon emissions as they scoot around the park.

Jackass Acres K9 Korral

Jackass Acres K9 Korral in New River, Ariz., is a park for the canines, and it uses 100 percent green operating practices. Every single item in the park, from benches to water fountains, is made with recycled materials. The park also uses solar power for lighting and has plans for composting dog waste. It doesn't get much greener than that.

Valmont Park

Valmont Bike Park will open in Boulder, Colo., in June 2011. The 40-acre bicycle park, within the 132-acre park site, is especially exciting for the city's huge cycling community. The park will have all the usual details: eco-friendly toddler areas, dog parks and fields for picnics, but it will also feature more than 30 bike trails, trick spots and jump-offs for people to enjoy — all while using renewable resources to conserve electricity and the environment.

Denali National Park

Denali National Park in Alaska is one of the most beautiful parks in the country. You can't go wrong with 6 million acres of wilderness filled with grizzly bears, wolves and deer. The park uses green shuttle buses to cart tourists around, and the recently reopened Eielson Visitor Center follows strict green building codes, paying close attention to sustainability.

Glacier National Park

Glacier National Park in Montana makes the list, thanks to its innovations with climate-change education. Since 1850, many of the park's glaciers have shrunk substantially, and the park is doing its best to teach people about the effects of global warming, all the while keeping its own sustainable practices.

Green River Reservoir State Park

Green River Reservoir State Park in Vermont is one of those locations that's green without flaunting it. Like much of Vermont, this park prides itself on beautiful rivers, lakes and native wildlife. Green River Reservoir has been using sustainable wildlife management for years now, and it's a wonderful place to visit if you're in the mood to canoe upriver.

North Cascades National Park

North Cascades National Park in Seattle has created an environmental learning center that's completely green. Eighty percent of the construction was made with recycled goods; there's a rooftop rainwater harvest, green lighting and solar energy. The best part is the center is open to the public. Designed to inform visitors about green building and other topics — and as a general meeting place — this is a must-see if you're in the Seattle area.

Eden Park

Cincinnati's Eden Park has been going green since its pilot solar and wind energy project that began in 2006 with a goal to demonstrate the effectiveness of using renewable energy to power city buildings. The staff has undertaken at least 14 initiatives to ensure that the park is one of the leaders in innovative design. From solar panels to solar garbage cans, Eden Park has it all. Park managers have also planned to plant more than 3,000 trees per year (1,000 more than they normally do). There are recycling centers available so visitors can do their part.

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