It's a nationwide birthday celebration, and you're invited. The National Parks Service marks its 98th birthday with a free entrance day for visitors of its parks and recreational areas across the country. Our Grand Canyon State is home to three, including its namesake. The Petrified Forest National Park and Saguaro National Park round out the trio when it comes to officially designated parks. Lucky for Arizonans, however, our state is also full of a variety of national monuments, historic areas, and protected areas -- all of which fall under the umbrella of this annual birthday freebie.