This is part of Airplane Mode, a series on the business—and pleasure—of travel right now.

On a hot June day, I was trapped on a packed shuttle bus—so packed that my nose was brushing the armpit of the man next to me. I was visiting Zion National Park in Utah. The owner of the armpit was a New York City schoolteacher, there with three friends as part of a bachelor party. They were headed to Las Vegas next—if we ever managed to get off the shuttle bus.

We were stuck because a van had slipped from Zion Canyon Scenic Drive and was hanging halfway off a ledge over a river. No one was hurt, but we had to wait for the van to be towed before we could move on and be dispelled at a shuttle stop to swarm around the park. Even when traffic is not being stopped because of a freak incident, to visit Zion is to often be jam-packed next to other people. It was the third most popular national park that year: 2017. To add to the chaos, I was there the week before July Fourth.

Sometimes you just can’t avoid crowds if you want to see what everyone else wants to see. The National Park System reported nearly 312 million visits last year, with 26 percent of visits concentrated at the eight most-visited parks. During the pandemic, some parks were so popular that the National Park Service required visitors to make reservations just to get inside. Glacier and Rocky Mountain National Parks continue to require advanced bookings between May and October, and if you want to take a drive up Cadillac Summit Road in Acadia or brave Angels Landing in Zion, you may need a permit.

I get why people flock to these parks: vistas, nature, splendor ahoy! And we spend a lot to see them. National parks generated $42.5 billion in 2021, according to the National Park Service. That figure includes $20.5 billion of visitor spending in communities within 60 miles of a park, on everything from hotel rooms to groceries to keychains to national park–inspired beers brewed right outside park gates.

Technically, these numbers come from a panoply of parks. There are what I call the “capital-N, capital-P National Parks,” which encompass “large land or water areas” and have been elevated to National Park status by Congress. There are 63 of these, including the ones you probably think of right off the bat—Yellowstone, Grand Teton, Grand Canyon, Yosemite—and some gems you might not be as familiar with, such as Indiana Dunes National Park along Lake Michigan, Cuyahoga Valley National Park in Ohio, and even St. Louis’ Gateway Arch.*

But if you want to truly avoid crowds, you will most likely find the same kinds of vistas, nature, splendor, and awe within the other 363 parks that the National Park Service oversees. These include lakeshores, battlefields, memorials, parkways, and monuments, and visiting enables you to experience America while also keeping your nose out of a stranger’s armpit.

There’s an easy way to find these lesser-known destinations: the Passport to Your National Parks, a $12.95 spiral-bound booklet first created in 1986. It lists all sites overseen by the National Park Service, and upon next printing will include the newest: the Baaj Nwaavjo I’tah Kukveni Grand Canyon National Monument, designated as such by President Joe Biden on Aug. 8. Every time you visit a park, you stamp your book, with each stamp including the name of the park, its location, the date, and sometimes specifics like which section of the park you visited. This is different from the America the Beautiful entrance pass, which grants you access into the parks that do charge a fee for a year—though most of the 426 national park units are free.

These other kinds of parks aren’t necessarily lesser or even smaller. The new monument is nearly 1 million acres. (And some of them can still get crowded: the busiest national park unit I’ve been to this year wasn’t a capital-N, capital-P National Park, but Devils Tower National Monument in Wyoming.) It takes an act of Congress to upgrade something to a national park, a designation that is almost always given to a park already run by the National Park Service. But presidents can designate national monuments on their own, on already owned federal ground, that might not get bipartisan approval. One reason behind Biden creating the Baaj Nwaavjo I’tah Kukveni Grand Canyon National Monument was to protect that land from uranium mining, and as you can imagine, some Republicans are pissed.

In July, Biden also designated a national monument for Emmett Till and Mamie Till-Mobley, because the National Park Service also caretakes land connected to the worst parts of the country’s history. My passport has also led me to the Sand Creek Massacre National Historic Site in Colorado; the Fort Smith National Historic Site in Arkansas, which is part of the Trail of Tears National Historic Trail; and Manzanar National Historic Site in California, where more than 10,000 Japanese people and Japanese American citizens were incarcerated during World War II. These sites are not easy visits, but they are an important piece of America’s past, and just as important as—or even more important than—watching Old Faithful spout off at Yellowstone.

I bought my Passport to Your National Parks in 2017, on the first day of the monthslong cross-country road trip that included that Zion trip where I became well acquainted with a stranger’s armpit. Being a stamp-seeker has changed the way I see the U.S., and led me to some less crowded spaces, even when traveling in peak summer. As of last week, I’ve now been to 221 sites, most collected on cross-country road trips, including the 29 I saw in July when I drove from New Jersey to California and back again. And yes, the stamps I collected on my last trip included some capital-N, capital-P National Parks: In that month, I kayaked through caves at Channel Islands National Park in California, walked among fields of fossilized wood at Petrified Forest National Park in Arizona, hiked up Lehman Creek Trail to be greeted by deer, turkeys, and a rattlesnake in Great Basin National Park, and stayed FAR AWAY from the bison at Theodore Roosevelt National Park in North Dakota.* (Another important travel tip: Bison can and will gore you.)

But I also walked my dog along the Jacks Fork River at the Ozark National Scenic Riverways in Missouri, watched shore crabs scuttle along the tidepools at Cabrillo National Monument in San Diego, and learned about fur trading (and saw a few prairie dogs) at the Knife River Indian Villages National Historic Site in North Dakota.

Near the end of my road trip, after I’d hiked Effigy Mounds National Monument in Iowa with my dog—and got my passport stamp—I stopped at a gas station to fuel back up for the rest of the drive home.

“Why would someone from New Jersey want to visit Iowa?” a woman yelled at me as I waited for my tank to fill.

“Because there’s something neat to see in every state!” I said.

You can get a list of all these sites online, and the National Park Service has an app. But my passport has become a tangible, running diary of my adventures. When someone asks me for my favorite national park, I’ll say Bandelier National Monument in New Mexico, where I camped under the stars next to two teens who were arguing about a fake ID being swiped within the first few days of their trip; or Pictured Rocks National Lakeshore in Michigan, where I stood on the lip of a 200-foot-high sandstone cliff overlooking Lake Superior, without any warning signs or guardrails or gaggles of people to interrupt my thoughts of “This is neat!” or get in the background of the selfie I took. (I am still a tourist, even if no one’s around.) I wouldn’t have known these places existed, or had those experiences, without my little blue passport. It’s a reminder of all I’ve visited—and how much I still have left to see.