Total height versus the tallest drop
The biggest source of disagreement is what counts as the waterfall. Total height is the vertical distance from the top of the highest drop to the base of the lowest, including any cascades and pools in between. Tallest single drop is the biggest uninterrupted fall within that.
Yosemite Falls in California shows the gap well. Its total height is usually given as 2,425 feet, but that is three sections: Upper Yosemite Fall, the middle cascades and Lower Yosemite Fall. The upper fall alone is about 1,430 feet. Both numbers are correct answers to different questions.
Where is the top, and where is the bottom?
Even a single drop has fuzzy ends. The top may be the lip where water leaves the rock, or the head of the rapids above it. The bottom may be the pool surface, the point where the water first hits rock, or the end of the cascade below. On a steep cascade these choices change the answer a lot.
Tiered falls add another question: are the tiers one waterfall or several? When a tier is separated by a long pool or a stretch of flat stream, most databases list it separately. When the tiers run straight into each other, they are usually counted together.
How heights are actually measured
- Topographic maps. Reading the contour lines at the top and bottom of the fall gives an estimate, limited by the contour interval, often 20 or 40 feet on USGS topo maps.
- Lidar elevation data. Airborne laser surveys now cover most of the United States at about one-metre resolution, and give much better numbers for falls in open terrain. Dense spray and overhangs still confuse them.
- Laser rangefinders and surveying. Measured on site, the most accurate method, used for record claims.
- Estimates. Many heights in older guidebooks and signs are eyeballed or copied from an earlier source. Round numbers like 100 or 200 feet are often estimates.
The heights on this site
The heights on our map come from OpenStreetMap, where volunteer mappers record a height tag when they have a source, often a sign, a guidebook or a published database. We convert them to feet and show them as they are. Where no mapper has recorded a height, we say so rather than guess. Treat any single height as approximate, and expect well-known falls to have a published figure that differs somewhat.
The height filter on the map uses these figures, so a fall with no recorded height does not appear in a filtered list even if it is large. Switch to Any height to see everything. For the biggest falls, see the tallest waterfalls in the US.
Height is not the same as impressive
A tall waterfall on a small stream can be a thin ribbon for most of the year, while a short fall on a big river can be thunderous. Volume, the shape of the drop, and the setting all matter as much as height. Niagara Falls is under 200 feet tall, far shorter than hundreds of mountain falls, and moves more water than any of them.