Every year, the National Parks Service waives normal admission fees on certain special periods, including President’s Day weekend, National Public Lands Day, and Veterans Day. The exact number of fee-free days varies from year to year. Where 2015 saw 9 free days, because 2016 marks the National Park Service's 100th year anniversary, this year the entire week is free!

According to NPS spokesman Jeffrey Olson, this awesome tradition to get more people outdoors started in 2009 by then-Secretary of the Interior Ken Salazar. The free admission was intended “to give people a break during the depths of the recession,” says Olson, in addition to giving people a chance to experience U.S. national parks for themselves.

National Park Week runs from April 16-24, and along with Martin Luther King Jr. Day, National Park Service Birthday, National Public Lands Day, and Veterans Day, this is that special time of year when you can get free admission to the more than 500 parks in the system across the United States.

Additionally, if you happen to have a child in fourth grade this year, your entire family is welcome to a free admission at all parks for a full year. This special promotion, called Every Kid in a Park, was launched in September as part of the 100th anniversary and a nationwide campaign to get children into the outdoors.

According to the National Park Services website, “the fee waiver includes entrance fees, commercial tour fees, and transportation entrance fees. Other fees such as reservation, camping, tours, concession and fees collected by third parties are not included unless stated otherwise.”