I first fell in love with topographic maps about 12 years ago. I’d scored a dream job with the National Park Service, performing archaeological surveys deep in the backcountry of Sequoia/Kings Canyon National Park for weeks at a time. Every morning, our crew leader would have us unfold our Mt. Clarence King or Kearsarge Peak 7.5 minute quadrangle maps, and we’d plot out the day’s off-trail survey. At lunch, we’d do the same, this time trying to figure out where the hell we were, using contour lines and shooting bearings of nearby peaks with our incredibly cool orienteering compasses. Nobody carried a GPS. The maps were like little miracles to me. The little boy in me was eternally fascinated.

I knew nothing about topo maps then. I was perplexed at how they were made, and wondered how much of the country had been mapped to that level of accuracy. For the next few years I worked as an archaeologist, occasionally using topos in field surveys, drawing site maps of my own, still befuddled how a two-dimensional paper map could depict the contours of the earth so well.

Here are five things you may not have known about topo maps (though you’ve likely suspected #5):

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1. Scientists have actually drawn topo maps of the surfaces of other planets. Mercury, Venus, Mars—all mapped. You could plop down on the surface of those places, and, well, lord knows what your compass would be doing (and you’d definitely be dead), but you could in theory, hike around for awhile with a decent idea of where you were. Our moon has been topo-ed too. Of course, all the best campsites on the moon have been booked like a year in advance, and you can forget about scoring a weekend site up there until 2025.

2. The U.S. Geological Survey (USGS) has been making and compiling topographic maps since 1884. That’s a long time! They finally finished mapping every square inch of the lower 48 states in 1991, and have published tens of thousands of topo maps in their history. You can actually access thousands of historic topographical maps through the USGS’s Topoview website. Want to compare topos of Mt. Whitney from 1919 and 1994? See how the Lake Tahoe basin has developed in the last 60 years? Topoview’s got the goods. I’ve spent way, way too much time on this website already.

3. Until about 1950, topographic maps of the U.S. were made from beautifully-engraved copper plates. At first, these plates were engraved from field drawings made by surveyors. Eventually, aerial stereophotography replaced the hand-drawn field maps, before new techniques nixed the copper engravings altogether. But for a few decades, USGS topos were pressed from gorgeous copper plates, adding an even cooler bit of alchemy to the map-making magic. I kind of wish they still were. Some of those copper plates were preserved, and have been sold to the public for display.

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4. Ever wonder how accurate 7.5 minute USGS quadrangles are? I always did. The vast majority of times you’re in the backcountry, “pretty accurate” is just fine for maps, provided you’re on a trail, of course. But still, I was always curious—is this bridge on the map, really, exactly right where the map says it is? Turns out, USGS topo maps use the National Map Accuracy Standards. This means that 90 percent of the horizontal points tested by field survey teams are accurate to within 40 feet. Vertical points, to within half a contour line, or five feet, based on standard 7.5 minute, 10-foot contour lines. So, yeah. That bridge is pretty much where it says it is.

5. Using a topo map temporarily turns you into a badass explorer. Look – I LOVE my Gaia GPS app. Love it. Wouldn’t go the backcountry without it. But I still pull out my topo [ed. note: for god’s sake, always bring a paper map] and compass and try to plot my location because it makes me feel like an honest-to-god adventurer. Plus, they make people using them look cool as hell, as I remind my wife every time I pull a map out of my pack.

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Bonus: 6. Hey, you stuck around to the end. Nice job. Here’s one last localized topo fact. The back cover of Adventure Journal Quarterly features a section of a U.S. topo map that relates somehow to a place featured in the magazine. Sometimes the connections are direct, sometimes not. See if you can figure them out!

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