Bob's Rough Guide to the National Parks:  Social Distancing Index

Overall, the parks are good places to go, with two huge caveats:  first, many park trails do not have suitable places to pass people at a distance who are going the other way, or the same way at different speeds.  You're fine in most parks until then, but forced to close quarters when that happens, as it will.  The other issue is popular viewing spots.  The scenic overlooks, the Old Faithfuls, etc. all draw crowds, and it can be hard to maintain distance when there are too many people per square yard of vista area.

What you need then are parks where more off-trail travel is acceptable, where the crowds are low enough to make trail or vista encounters infrequent, or where what you go to see is viewable from a wide area rather than a limited number of small spots.  Hints for trails:  in general, the more elevation change, or the higher the actual elevation, the less chance for distancing.  Those trails often involve switchbacks; the more a trail had to be "made," the less likely you can get off it to let someone pass safely.  Trails through forests, meadows, grasslands, dunes and low hills are better bets.  Of course, don't go off trail where resource damage is an issue.

Individual parks will each make their own adjustments to procedures when they reopen, so things will be different in some cases from what you're familiar with.  Don't be surprised if some areas are closed, some have "one way" signs, some have time limits, and some have a quota or reservation system.

Below is a general guide where 1 = little or no distancing possible and 5 = excellent.  After that are some park-specific thoughts.  Your mileage may vary.  If people want to make well-informed revisions to this rough guide, go ahead and turn it into a wiki to do so.

Cave Parks - 1; mostly guided tours, can't be socially distant as now managed

          Examples:  Carlsbad, Wind, Jewel, Mammoth, Oregon Caves

Mountain Parks - 2; many have steep trails where it's hard to pass safely

          Rocky Mountain, Glacier, Mount Rainier, Yosemite

Canyon Parks - 2; many have steep trails where it's hard to pass safely

          Bryce, Grand Canyon, Zion

Mixed Mountains & Forest - 2.5; more pass-able trails than all-mountain parks

Olympic, Great Smoky Mountains, Redwoods, Shenandoah

Coastal Parks - 3; can often avoid others, but access may be an issue

          Acadia; Everglades; Biscayne Bay; Channel Islands

Desert Parks - 4 to 5; lots of open spaces to roam

          Death Valley, Joshua Tree, Saguaro, Mojave

Acadia - mixed.  Some trails are iffy, but there are opportunities:  the bike paths, portions of the coastline, Cadillac Mountain once you're on top, portions of the forested areas.

Arches - poor near the arches, moderate elsewhere; the catch is, the arches is where you and everyone else most want to go.  You should stay on the trails near the arches in most cases, in part to avoid damaging the cryptobiotic soil, but the people level here makes distancing challenging come passing time.  In some other areas, like near Courthouse Wash, there are areas where you can roam somewhat freely (still being careful of that soil, though; stay on rocky surfaces).

Badlands - not bad.  The crowds here are low enough that if you avoid peak season you should be fine in most cases.

Big Bend - mixed.  Many of the trails don't make sidestepping easy, but the crowds are low enough to give you a fair shot.

Biscayne Bay - once underwater, you're fine.  The visitors center and small on-land areas aren't so good.

Bryce Canyon - mixed, but low in season.  Another place where off-trail is often unsafe, and where there are a lot of small overlooks.  There are some good spots:  walking along the rim gets you away from the crowds, and some trails like the Fairyland Loop are lightly traveled.

Canyonlands - good other than at overlooks on the east side of the park.  Lots of dirt roads and low-use trails.

Capitol Reef - pretty good.  While a few of the most popular trails will be busy, there are many with low hiker counts, and there's lots of backcountry and side road acreage to explore.  Cathedral Valley and Notom Road in particular have great views with low crowds.

Carlsbad Caverns - poor; anything requiring a guided tour is bad.  The few places you can do independent walking still require staying on the paths in the cave with nowhere to bail out.  The entrance is a pinch-point, too.

Channel Islands - once there, good, it's getting there that's the issue.  It's a handful of offshore islands, and the normal way to get there is via a crowded boat.

Crater Lake - mixed.  It has a lot of popular overlooks, which will be busy, but in between them are opportunities.

Death Valley - excellent.  Outside of a few scenic overlooks and narrow sections of some trails, it's easy to avoid people in most of the park.

Denali - relatively low unless you like long hikes.  For one thing, access to the core of the park is either multi-day backpacking or taking a used school bus; no distancing on the latter.  The outer areas have sights, but are along a narrow corridor that will be moderately busy.

Everglades - fair on land, good in water.  The major foot paths will be busy, but not all trails.  If you get out in a boat on the water, you'll be fine, it's just making sure the boat is sanitized if you rented it.

Glacier - mixed.  Some trails allow for distancing, others don't.  Likewise, some scenic overlooks are small, others let people spread out. 

Grand Canyon - fairly good on the rim, bad on trails into the canyon.  The trails have few bail-out areas, since most are cut into the canyon walls.

Grand Teton - good for the most part.  Has some trails where passing is a problem, plus some busy scenic overlooks, but also has lots of open space, bike paths, and trails where stepping out is easy.

Great Smoky Mountains - mixed; it all comes down to what trail you're on.

Great Sand Dunes - good; there are some trails, but mostly you just wander over the dunes, so just go where others aren't.

Jewel Cave - poor.  Guided trips, so no distancing possible.

Joshua Tree - pretty good.  Like other desert parks, you're able to wander about the landscape pretty well.

Lassen - good.  Low visitor count makes avoiding people easier, although some places like the Bumpass Hell trail might get busy and have boardwalk issues.

Mammoth Cave - poor; all done on guided walks.

Mesa Verde - poor.  To see many of the ruins, you need to be escorted as part of a group; just the opposite of what's needed.  Even when on your own, you're still going where everyone else is.

Mount Rainier - mixed.  Lots of trail mileage, but the people tend to concentrate in a small portion of them, e.g. Paradise.  In season, you'd want to avoid going off trail to protect the delicate tundra flowers.

Painted Desert / Petrified Forest - mostly good.  While there are places where you need to stay on trails and thus distancing is harder, much of the park is open to cross country wandering, especially the Painted Desert portion.

Redwoods - good; there's plenty of space to bail out into the forest briefly if you encounter someone on a trail.

Wind Cave - poor.  Guided trips, so no distancing possible.

Yellowstone - relatively low, unlike its neighbor, Grand Teton.  The primary thermal areas are bad, since you have to stay on the boardwalks; nowhere to hide.  Same thing with overlooks of the larger waterfalls.  Some trails are stay-on problems, but the lesser-used trails have opportunity to separate.  Unfortunately, the more likely a trail is to avoid people, the more likely you're at risk from grizzlies or will need to make it a really long hike.

Yosemite - low in the valley, better elsewhere.  In the valley, there's just too little space per person to spread out well.  You have to get to the high country, or the Wawona or Hetch Hetchy areas to thin things out.

Zion - low in the main canyon and at overlooks in other areas, pretty good in less-visited portions.