Topographic map of the United States: the USGS map, explained

What is the USGS topographic map?

USGS, the U.S. Geological Survey, is the federal government's earth-science and mapping agency, part of the Department of the Interior. Since the 19th century it has surveyed the country and published the topographic map that generations of American hikers, hunters, foresters and surveyors know simply as "the quad": the sheet with the contour lines, the trails, the streams and the name of every peak and pass.

The map most people picture is the 7.5-minute quadrangle, drawn at 1:24,000. One inch on the map is 24,000 inches, or 2,000 feet, on the ground. Each quad covers 7.5 minutes of latitude by 7.5 minutes of longitude, a rectangle that shifts in size across the country but is always the same shape. It took the Geological Survey decades to cover the lower 48 states at this scale, sheet by sheet, before digital production took over.

Because USGS is a federal agency, its maps are a work of the U.S. government and carry no copyright. They are free to view, download and reuse. The same survey data now feeds the digital USGS Topo basemap, the seamless map shown on this page, which redraws itself as you zoom from a whole state down to a single trail junction.

How the map is made, and which USGS map is which

USGS maintains The National Map, a set of national databases built from lidar elevation data, aerial imagery, hydrography and place names. Contours, roads, trails, water features and labels all live there as data. The USGS Topo basemap on this page is drawn from that data by software at a series of zoom levels, refreshed as the underlying data changes rather than sheet by sheet.

That makes it a different product from US Topo, the current quadrangle series, which is still published as individual maps laid out on the historical 7.5-minute grid, one GeoPDF per quad. The cartography is close, since both draw on the same National Map data, but they are not the same file. Here is the family in one table.

• USGS Topo (National Map) (Multi-scale, digital): The seamless basemap redrawn from the National Map database at every zoom, public domain like everything USGS publishes. This is the Topo layer on this page and in Traverse.
• US Topo (1:24,000): Individual quadrangle maps in GeoPDF format, laid out on the historical 7.5-minute grid. Free to download by quad name from the USGS store.
• Historical topographic maps (Mostly 1:24,000, some 1:62,500): Scans of the original hand-drafted quadrangles USGS published through the 20th century, before digital production. Browse them by place and date in topoView.
• Imagery, imagery + topo, shaded relief (Multi-scale, digital): Three more National Map layers, built from the same aerial photography and elevation data as the Topo basemap. All three are on this page and in Traverse.

How to read the USGS topo map

The symbols below are the ones that show up on the National Map's Topo basemap in mountain terrain. Each one has a button that moves the live map to a place where you can see it for real.

• Brown contour lines, labeled in feet: Each line joins points of equal elevation, in feet, not meters. The gap between labeled lines is the contour interval, and it is not printed on screen: read it from the difference between two consecutive numbers. Around Half Dome the labels climb in 80-foot steps, so the interval is 40 feet. Near Mount Washington's summit the labels climb in 20-foot steps.
• Pale green wash: Tree cover. It thins out and stops at treeline, which on this basemap is a useful, if soft, edge between forest travel and open alpine ground.
• Light blue fill: Lakes, ponds and wide rivers. Jenny Lake and Leigh Lake sit right below the Teton Range this way, filled in solid pale blue against the white and green of the valley floor.
• Blue dotted fill: Permanent snow and glacier ice. Mills Glacier below the east face of Longs Peak is drawn this way, a checkerboard of blue over the white ground, with the ice edge as a thin blue outline.
• Green dashed line with tick marks: Foot trails. The Mist Trail and John Muir Trail through Yosemite's Little Yosemite Valley are drawn this way at hiking zooms. Zoom in further and the same trail turns into a solid green line, and zoom out and it can drop off the map entirely, so check more than one zoom level before you trust a route.
• Salmon-red road line: A numbered state or federal highway, shown with its shield. South Entrance Road into Grand Canyon National Park, signed as Arizona 64, is drawn this way. Thinner tan lines nearby are unpaved or local roads.
• Solid bright green line: A national park or forest boundary. The line runs along the edge of Grand Canyon National Park here, with the park's name lettered in green capitals just inside it.
• Yellow dash-dot line: A wilderness or national forest boundary, a different line from the park boundary above. It crosses Longs Peak just below the summit ridge, a reminder that an administrative line on the map can run straight through terrain that looks continuous on the ground.
• Elevation numbers in feet: Named summits, passes and lake surfaces carry their elevation in feet, either beside the name or set directly on a contour line. Half Dome's summit is labeled this way, with the number giving you a precise height that saves you counting contour lines by hand.
• Small orange square icon: A named point of interest. Nelson Crag, a shoulder of Mount Washington's summit cone with a junction of trails, is marked this way, with an orange icon and a label rather than a building symbol.

1. Start with the shape: Switch to the shaded relief layer and find the ridgelines and drainages before you look at a single contour. It is the fastest way to see how a mountain is built.
2. Then read the steepness: Zoom in until contours appear and look at their spacing along your line. Work out the contour interval first, from the gap between two labeled numbers, because it is not printed anywhere on screen and it is not the same on every quad.
3. Check every height in feet: Summits, passes and lakes carry their elevation in feet. Subtract the start from the high point and you have your climb before you have opened any other tool.
4. Expect the map to change with the zoom: Trails switch from a dashed line with tick marks to a solid line as you zoom in, hillshade fades in and out, and small roads and buildings only appear close in. Check a feature at more than one zoom before you rely on it.

Browse the live Topo map

This page loads the real USGS tiles in an interactive map, with Topo and Imagery + topo and Shaded relief and Imagery and shortcuts to Grand Teton (Teton Range, Wyoming), Half Dome (Yosemite National Park, California), Mount Rainier (Cascade Range, Washington), Grand Canyon South Rim (Grand Canyon National Park, Arizona), Longs Peak (Rocky Mountain National Park, Colorado), Mount Washington (White Mountains, New Hampshire).

USGS map words, in plain English

A handful of survey terms cover most of what shows up on a USGS quad. Here is what they mean.

Quadrangle

The rectangle of land covered by one USGS topographic map sheet, usually just called a "quad."

7.5-minute quadrangle

The standard USGS quad, covering 7.5 minutes of latitude by 7.5 minutes of longitude at a scale of 1:24,000.

Contour interval

The elevation difference, in feet, between one contour line and the next on a given quad. It varies from quad to quad.

Index contour

A heavier contour line, carrying its elevation, that makes it easier to count intervals across a slope.

Benchmark

A surveyed point of known elevation, marked on the ground with a metal disk and noted on the map as "BM" with its height.

Spot elevation

A single point's height printed on the map, on a summit, pass or road junction, not read off a contour line.

Datum

The reference surface that all coordinates or elevations on a map are measured from.

NAD83

North American Datum of 1983, the horizontal reference used on current USGS maps.

NAVD88

North American Vertical Datum of 1988, the height reference used on current USGS maps.

Township and range

The rectangular grid the federal government used to survey and describe land across most of the country outside the original states.

Section

One square mile, one thirty-sixth of a township, the smallest standard unit of the township-and-range grid.

Declination

The angle between magnetic north and true north at a given place, printed in the margin of a paper quad.

Saddle

A low point on a ridge between two higher points, shaped like the seat of a saddle in the contours.

Col

Another word for a saddle or pass on a high, narrow ridge.

Cirque

A bowl-shaped hollow at the head of a valley, carved by a glacier that has since retreated or vanished.

Bench

A relatively flat shelf on an otherwise steep slope, often a natural resting point on a climb.

Draw

A small, shallow drainage, less cut in than a gully or ravine.

Talus

Loose, broken rock piled up at the base of a cliff or steep slope.

Gap / notch

A low break in a ridge, similar to a saddle but often narrower and steeper-sided.

Switchback

A trail that zigzags up a steep slope rather than climbing it directly.

Check the map against the granite

A topographic map is an interpretation. Aerial imagery is the evidence it was built from. USGS joins its aerial and satellite photography into one seamless layer, and switching between it and the Topo basemap is a fast way to understand a piece of terrain you have never seen in person.

Try it on Half Dome. On the map, the summit is a tight knot of contours with the cables route traced as a dashed line up the shoulder called Sub Dome. On the photo you can see the bare granite face itself: the sheer northwest wall in shadow, the rounded back side the cables climb, and the tree line running up against the rock.

The imagery is a snapshot too, flown on a particular date, and different areas can be years apart. It shows you the ground, not this week's snow or a downed tree across the trail.

What the map does not tell you

• It shows the ground, not the conditions. Snow, wildfire closures, a washed-out bridge or a locked gate are not on any topographic map.
• The contour interval is not printed on screen and is not the same everywhere. Read it from two labeled contours before you trust a slope by eye, and expect it to change from one quad to the next.
• A trail on the map is not a promise. USGS trails carry no difficulty rating or current condition, and a route can be rerouted, washed out or officially closed without the map catching up.
• This seamless basemap is a cartographic simplification of the underlying data. It does not carry every symbol from a printed quadrangle, such as the declination diagram or a full township-and-range grid, and it does not have a fixed publication date the way a numbered US Topo edition does.

Use the USGS map in Traverse

Traverse is a mountain mapping app for the web and iPhone. All four USGS National Map layers are in it, drawn on real 3D terrain, alongside the layers a flat topo map cannot give you.

• The USGS map in 3D: The same contours draped over the actual terrain, so a wall of tightly packed lines looks like the cliff it is.
• Slope angle on top: Shade everything over 30 degrees across the USGS map to see avalanche terrain and the lower-angle way around it.
• Recent snow and glacier context: SnowSight shows satellite-observed snow cover with its date. GlacierIQ adds glacier outlines, ice flow and a crevasse-susceptibility index.
• Routes, GPX and offline: Draw a route or import a GPX, get distance, ascent and a profile, then download the area for use without signal.

A Traverse account is free and includes the Traverse, Summer, Winter and Satellite maps with slope angle and aspect. Official national maps, including the USGS maps, are part of Traverse Pro.

Create a free Traverse account · Download Traverse for iPhone

Frequently asked questions

Are USGS topographic maps free?

Yes. USGS is a federal agency, and maps produced by the U.S. government are a public domain work with no copyright. You can view, download and reuse them freely, including the current digital editions and the scanned historical quads. You can browse the live basemap on this page for free.

What is a 7.5-minute quadrangle?

It is the standard USGS topographic map unit: a rectangle covering 7.5 minutes of latitude by 7.5 minutes of longitude, drawn at 1:24,000. Nearly the whole country has been mapped at this scale, one quad at a time, and the current US Topo series still follows the same grid.

What is the contour interval on a USGS topo map?

It depends on the quad. Steep mountain terrain commonly uses a 40-foot interval, and gentler terrain often uses 20 feet or 10 feet. The interval is not printed on the digital basemap shown on this page, so read it from the gap between two labeled contour lines.

Where can I download USGS topo maps?

Current US Topo quadrangles, as free GeoPDFs, are available from the USGS store by searching for a quad name or location. Scanned historical editions, from the same area at different dates, are in USGS topoView.

What is the difference between US Topo and historical topographic maps?

US Topo is the current quadrangle series, produced digitally from USGS's National Map database and refreshed over time. Historical topographic maps are scans of the earlier, hand-drafted quads USGS published through the 20th century, before digital production. Both follow the same 7.5-minute grid and the same 1:24,000 scale.

What scale are USGS topographic maps?

The standard is 1:24,000: one inch on the map equals 24,000 inches, or 2,000 feet, on the ground. Older and smaller-scale series exist, such as 1:62,500 and 1:100,000, but 1:24,000 is what most people mean by "the USGS quad."

Are heights on USGS maps in feet or meters?

Feet, measured against the North American Vertical Datum of 1988 (NAVD88). Horizontal coordinates use the North American Datum of 1983 (NAD83) on current editions.

Can I use USGS topo maps offline?

The USGS website and store need a connection, and a downloaded GeoPDF is a large file to carry on a phone. Traverse lets you save a region of the USGS map, with your route and terrain layers, for use without signal.

Sources

• USGS National Map
• US Topo, the current quadrangle series
• USGS topoView, historical topographic maps
• Topographic map symbols reference
• The USGS Store, order and download maps
• Are USGS topographic maps copyrighted? (USGS FAQ)