You’ve probably held one today. Or maybe it’s been a few weeks since you’ve seen a "C-note" in the wild, given how everything is digital now. But the back of the hundred dollar bill is actually one of the most sophisticated pieces of printing in human history. It isn't just green ink on paper. Most people think they know what’s back there—Independence Hall, right? Sure. But do you know what time it is on the clock tower? Or why there are tiny yellow 100s scattered like confetti?
Money is weird.
The $100 bill is the most circulated U.S. banknote globally. More of these live outside the United States than inside. Because of that, the U.S. Bureau of Engraving and Printing (BEP) turned the reverse side into a topographical map of anti-counterfeiting tech. It’s a mix of 18th-century history and 21st-century physics.
What’s Actually On the Back of the Hundred Dollar Bill?
At first glance, it’s Independence Hall in Philadelphia. That’s been the standard since 1928. Before that, the back of the hundred looked wildly different, featuring vignettes like "Commerce" or even mythological figures. But the 2013 redesign—the one with the "Blue Ribbon" on the front—completely overhauled the reverse side.
Look at the clock tower. On the older bills, the time was set to 4:10. On the newest Series 2009 and later notes, the time is 10:30. Why? Nobody really knows. The BEP hasn't given a definitive "historical" reason, though some amateur sleuths tried to link it to the signing of the Declaration of Independence. Honestly, it’s likely just a design choice to make the engraving clearer.
The engraving itself is a masterpiece. It shows the rear view of the building. You can see the individual bricks if you have a magnifying glass. To the right of the hall, there’s a large, vertical "100" in gold ink. This isn't just for people with poor eyesight. This is high-visibility, color-shifting ink meant to help people identify the denomination quickly in low light.
The Tiny Yellow Constellation
Have you noticed those tiny yellow numbers scattered in the "white" space?
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That is the EURion constellation. It’s a pattern of symbols incorporated into the design of many banknotes worldwide. If you try to scan the back of the hundred dollar bill on a modern color copier, the machine will literally stop working. It recognizes those yellow 100s as a "do not copy" command. It’s a digital handshake between the Treasury and companies like Xerox and Canon.
The Mystery of the "New" Independence Hall
The current image of Independence Hall on the back is significantly larger than the one used on bills printed between 1928 and 1996. It’s a different perspective. Back then, the building was framed by a small oval. Now, it’s a full-bleed vignette.
There’s a common myth that the people depicted walking in front of the building are famous historical figures. They aren't. They are just generic figures used to give the scene scale. But the detail is so fine that you can see the texture of the trees.
Wait. Let’s talk about the ink.
The green ink on the back is a specific, proprietary blend. It’s magnetic. If you have a powerful enough magnet—like a neodymium one—you can actually see the bill react. This is one way vending machines and high-speed counting machines verify that the bill is real. If the magnetic signature doesn't match, the machine spits it out.
How to Spot a Fake by Looking at the Reverse
Most counterfeiters focus on the front. They want to get Ben Franklin’s face right. They focus on the watermark. But they often get lazy with the back of the hundred dollar bill.
Check the lines. On a real note, the lines of the engraving are sharp and unbroken. In a "wash" (where a lower denomination is bleached and reprinted as a hundred), the ink often looks blurry or "flat." This happens because the paper—which is actually 75% cotton and 25% linen—absorbs ink differently once it's been chemically treated.
- Feel the paper. It should be "crisp" and have a raised texture.
- Check the "100" in the bottom right corner. It should shift from copper to green.
- Look for the microprinting. In the "100" in the corner, you should see "USA 100" repeated.
- Use a UV light. A pink security thread should glow on the left side (viewed from the front, right side from the back).
Actually, the security thread is visible from both sides. When you hold the back of the bill up to the light, you should see that vertical strip. It says "USA" and "100" in an alternating pattern. If that strip is missing or looks like it was drawn on the surface, you’re holding a piece of junk.
The Hidden "Gold"
The large gold "100" on the back isn't just about color. It’s about "Intaglio" printing. This is a process where the paper is forced into the recessed lines of an engraved plate under massive pressure. This creates the "feel" of the money. If you run your fingernail across the gold 100, it should feel rough. Counterfeits produced on standard inkjet or laser printers will feel smooth.
Is it possible to fake the texture? Some try by using "thermography," which uses heat to raise the ink. But it never quite feels the same as the $200,000-per-square-inch pressure used by the BEP.
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Why the $100 Bill is Changing Again
You’ve probably heard rumors about the "Series 2021" and future designs. The Treasury is constantly playing a game of cat and mouse with North Korean "supernotes"—high-quality fakes that are almost indistinguishable from the real thing.
The back of the note is likely to see more "white space" reduction in the next decade. Why? Because white space is where counterfeiters find room to play. The more intricate the engraving across the entire surface, the harder it is to fake.
Funny enough, Benjamin Franklin never wanted to be on the hundred. He actually had a lot of opinions about paper money—he even printed some himself for the Pennsylvania colony. He used to put deliberate misspellings in his bills because he figured a counterfeiter would "correct" the spelling, making the fake easy to spot.
Practical Steps for Handling Large Bills
If you’re a business owner or someone who handles cash often, don't just rely on the "pen." Those iodine pens only detect starch in regular paper. A sophisticated counterfeiter can coat fake paper in a chemical that fools the pen.
Instead, focus on the back of the hundred dollar bill.
- Tilt it: The gold 100 must change color. If it stays gold, it’s fake.
- Scratch it: Use your nail on the building’s engraving. You should feel the ridges.
- Light it: Hold it to the sun. The security thread and the watermark (Franklin's face) must be visible from the back.
- Magnify it: Look at the "USA 100" microprinting around the borders. It’s almost impossible to replicate with consumer-grade printers.
If you find a suspicious bill, do not put yourself in danger. Don't try to be a hero. Note the person's description and contact the Secret Service or local police. Once you turn it in, you don't get a "real" one back (which sucks, honestly), but it's better than getting caught trying to pass a fake yourself.
The back of the hundred dollar bill is a piece of art that we usually just shove into a wallet. Next time you have one, take thirty seconds to actually look at it. Between the EURion constellation, the intaglio printing, and the magnetic ink, there is a lot of science keeping that $100 worth $100.
Keep your eyes on the gold 100 in the corner. If it doesn't shift, it's not real. Check for the pink glow of the security thread under UV light. Always verify the texture of the Independence Hall engraving before accepting large sums of cash.