National Park Week - Free Admission

There are several days each year in which entrance fees are waved at the National Parks, the April event is coming up. April 22-26 is National Park Week, and admission fees are waved.
Other fee-free days are:

• August 25 - National Park Service Birthday
• September 28 - National Public Lands Day
• November 9-11 - Veterans Day weekend

For more information, check out the National Park Services site.
Note: Other fees such as reservation, camping, tours, concession and fees collected by third parties are not included unless stated otherwise.