lol, it would be easier if they were just under one land management agency, wouldn't it? Remind me to tell you of the time I worked for a National Forest, part of which was classified as a National Monument, bordering a National Park all with very similar names... and if that wasn't bad enough this national forest surrounded a state forest, which surrounded a county park... Imagine trying to explain to the public the difference, and it was important to do so because of all the different laws and regulations for each.
I worked in Sequoia & Kings Canyon National Parks, Curecanti NRA & Black Canyon of the Gunnison National Park, and Natural Bridges National Monument. Backpacked extensively in the first. The rest of my career has been working for neighboring National Forests and National Monuments managed by the FS. I've grown to appreciate USFS and BLM lands, they contain scenic gems not unlike the parks, but are generally much less crowded and less regulations.
I've visited the following parks (last one visited listed first):
Carlsbad Caverns
Guadalupe Mountains
Isle Royale (backpacked across the island over the course of a week)
Teddy Roosevelt
Saguaro
Channel Islands (backpacked Santa Cruz and Santa Rosa Islands)
Petrified Forest
Grand Canyon
Great Smokey Mountains
Joshua Tree (backpacked many times)
Pinnacles
Kenai Fjords
Yellowstone
Grand Teton National Park
Acadia
Wind Cave
Rocky Mountain
Badlands
Capitol Reef
Mesa Verde
Zion
Bryce
Black Canyon of the Gunnison
Arches
Canyonlands (backpacked once)
Death Valley
Great Basin
Yosemite (backpacked twice)
Denali
Redwood
Other NP managed sites:
Whitman Mission NHP
White Sands NM
Manzanar National Historic Site
St. Croix National Scenic Riverway
Pipestone NM
Chimney Rock and Scott's Bluff NM
Montezuma Castle NM
Tuzigoot NM
Mojave Trails NM
Sunset Crater NM
Wupatki NM
Walnut Canyon NM
Trail of Tears National Historic Trail
Santa Monica Mountains National Recreation Area
Cedar Breaks NM
Pipe Spring NM
Cape Cod National Seashore
Mojave National Preserve
Minuteman National Historic Site
Salem Maritime NHS
Point Reyes National Seashore
Rainbow Bridge NM
Devil's Postpile NM
John D. Rockefeller, Jr. Memorial Parkway
Bighorn Canyon National Recreation Area
Boston National Historic Park
John Muir National Historic Site
Devil's Tower NM
Mt. Rushmore NM
Jewel Cave NM
Fort Laramie National Historic Site
Oregon National Historic Trail
Pony Express National Historic Trail
Mormon Pioneer National Historic Trail
California National Historic Trail
Agate Fossil Beds NM
Navajo NM
Aztec Ruins NM
Colorado NM
Florissant Fossil Beds NM
Curecanti National Recreation Area
Muir Woods NM
Hovenweep NM
Canyon de Chelley NM
Organ Pipe Cactus NM
Lake Mead National Recreation Area
Golden Gate National Recreation Area
John Day Fossil Beds NM
Lincoln, Thomas Jefferson, Vietnam Veteran's, and Korean War Veteran's Memorials
Washington Monument, White House
Jamestown National Historic Site
Statue of Liberty NM
Independence National Historic Park
Cabrillo NM
Next up for me will likely be Olympic, Crater Lake, Mt. Rainier, North Cascades, and Glacier