Paper currency in America has a vast and complex history. Its various banknotes, limited editions, and errors have fascinated collectors and money dealers for centuries - and inspired not a few artists.
From the rarity of a banknote to the image on the face of the bill to the story behind why the legal tender is no longer in circulation, there are so many factors that can influence the value of paper money. Here's a look at some of the rare notes that are now worth a whole lot of cash - if you happen to find them lying around in an old attic or at the back of a thrift store.
Note: It's important to remember that the values listed below reflect bills that are in mint condition, or as close to uncirculated condition as possible.
What It's Worth: Sold at auction in 2018 for just over $2 Million
Why It's Worth So Much: The Grand Watermelon note is considered to be the holy grail of numismatics (the study or collection of coins, currency and medals). The oddly named bill got its moniker from the shape of the zeroes in the "1,000" label on the back of the note, as they resemble watermelons.
Only seven of these bills are known to still exist in various conditions, and the note's rarity plays the largest role in its steep price tag. General George Gordon Meade is honored with a place on the face of the bill.
What It's Worth: $10,000 to $200,000 and up
Why It's Worth So Much: A smaller denomination than the so-called $1,000 "Grand Watermelon" bill from the same series, the "Baby Watermelon" gets its name from the two zeroes on the back of the bill that, given their green hue and bulging shape, resemble smaller versions of said fruit.
There are currently only 35 known examples of this note in existence and available for private ownership. Even the most circulated and lowest-grade copies have brought in upwards of $10,000, so a bill in good or even mint condition could be worth several times more.
What It's Worth: $10,000 and up
Why It's Worth So Much: This bill, issued in the 1928 series of US federal reserve notes, features President McKinley on the face. The key feature is a star symbol at the end of the serial number, instead of the more common "A" (the "A" version is pictured above). While a $500 bill with a serial number ending in "A" might be worth a few thousand, the star symbol bumps that value up to $10,000 or higher, depending on its condition.
The 1934 series of $500 bills can also be worth a lot, although not nearly as much. 1934 was the final year that the $500 was printed by the treasury, and a pristine bill can go for as much as $1,800.
What It's Worth: $8,000 and up
Why It's Worth So Much: The $1,000 bill is the highest denomination printed during the 1918 series of bills that is still available to collectors (the $5,000 and $10,000 notes now only exist in museums). The note, which gets its name from the portrait of Alexander Hamilton on the face, has been sold for thousands of dollars in even highly circulated condition - meaning better-graded notes could fetch even more.