There are a lot of National Parks and Monuments in the US. I am unsure of the number. Five Monuments were added this year.
I will cover National Forests at another time.
National Parks are taken care of by the National Park Service. The Rangers are highly skilled, talented, hard working and the best looking people in the world.
If you get a chance, go to a National Park and look around. You will not be disappointed.

I will label the pictures from Wikimedia Commons as WC. Those pictures from the National Park Service I will label as NPS. This is because I am lazy.

Capitol Reef in the state of Utah  by, Bigtimepeace, WC.

Cassidy_Arch,_Capitol_Reef_National_Park Bigtimepeace WCRain forest Maple trees in Olympic National Park in the state of Washington  by, Kevin Muckenthaler, WC.

Hoh_Rain_Forest_Maples Washington Kevin Muckenthaler WCAmerican Samoa National Park  by, Peter Craig, NPS.

640px-Ofu_Beach_NPS Peter Craig NPSYosemite National Park in the state of California  by, User: AngMokio, WC.

640px-YosemitePark2_amk User AngMokio WCBig Bend National Park  by, eletico62, WC.

540px-Santa_Elena_Canyon electico63 WCEverglades National Park in the state of Florida  by, NPS. These are Cypress trees, except for the white bird.

640px-Everglades_National_Park_cypress NPSCuyahoga National Park in the state of Ohio  by, David Fulmer, WC. It’s called Blue Hen Falls.

640px-Blue_Hen_Falls David Fulmer WCThis last picture is of Biscayne National Park, in the state of Florida  by, NPS.

640px-Biscayne_NP_snorkeling NPS