National Park Week kicks off April 20 with free entry to every national park in America.

That’s not just capital NP national parks like Grand Teton and Olympic, but all 429 sites within the National Park System, ranging from national battlefields to seashores.

Entry fees are only waived that first day, but there are special activities planned throughout National Park Week (and many sites don’t charge entry fees anyway).

"With countless options of things to do and see, there really is something for everyone in our country’s national parks,” National Park Service Director Chuck Sams said in a statement.

What travelers should know:

What is the purpose of National Park Week?

The first National Park Week in 1991 marked the 75th anniversary of the National Park Service.

The next wasn't until 1994, but since then, it’s become an annual, presidentially proclaimed celebration across America’s ever-growing list of national parks, according to National Park Service spokesperson Kathy Kupper.

“During National Park Week, and throughout the year, I encourage people to discover and enjoy the natural, cultural, historical, and recreational opportunities available in national parks and through National Park Service community programs,” Sams said.

How long is National Park Week?

National Park Week spans nine days. It runs from April 20 through April 28.

Each day will spotlight a different parks-related theme.

• April 20: Discovery


• April 21: Volunteers


• April 22: Earth Day


• April 23: Innovation


• April 24: Workforce Wednesday


• April 25: Youth Engagement


• April 26: Community Connections


• April 27: Junior Ranger Day


• April 28: Arts in Parks

Travelers can find their nearest park through the National Park Service and National Park Foundation’s Find Your Park site.

Are national parks free on Earth Day?

Not this year. Earth Day is April 22.

Last year, it happened to coincide with the first day of National Park Week when parks offer free entry.

However, this year, the first day of National Park Week is April 20.

When are all US national parks free?

There are five more free entry dates this year:

• April 20: First day of  National Park Week


• June 19: Juneteenth


• Aug. 4: Great American Outdoors Day
 

• Sept. 28: National Public Lands Day


• Nov. 11: Veterans Day

Martin Luther King Jr. Day was also an entry-fee-free day in January.

Certain groups like military service members, veterans, and U.S. citizens and permanent residents with permanent disabilities are eligible for free entry any time of year. Fourth graders and their families are also eligible for free park visits through the Every Kid Outdoors program.

Visitors should note some parks charge fees for parking, access to specific facilities, and other things, even when entry fees are waived.

What activities can people do when visiting the national park?

Activities vary by date and location and can be found on the National Park Service’s event calendar. Junior Ranger Day events include the chance to build biplane models at Tuskegee Airmen National Historic Site in Alabama and learn about the history of dogs in Hidatsa villages and earn a BARK Ranger badge for their own pups at Knife River Indian Villages National Historic Site in North Dakota.

“Of course, we hope that kids will want to protect parks and want to make sure that we pass on parks to the future generations of kids, but in order to do that, we have to make sure that we are letting kids come to our parks to have fun, to fall in love with nature, to fall in love with history and culture,” Caitlin Campbell, interpretation and engagement coordinator for the National Park Service, told USA TODAY. “Our primary objective is to make sure that kids feel welcome in parks and know that parks are a fun and safe place where they belong.”

All year long, kids of all ages and abilities are invited to take part in the free Junior Ranger program in parks and online.

"They can find Junior Ranger programming probably pretty close to where they live," she said. "Any day of the year, they could celebrate (being a) Junior Ranger, but we hope that they celebrate during National Park Week."