Cash

Andrew Carnegie, one of the richest Americans ever, never carried any cash. He was once put off a London train because he did not have the fare.

President Kennedy never carried cash, borrowing from friends and often failing to pay them back. Despite his family's wealth, if you had a coffee and a doughnut with him, you would pick up the tab. He also donated his presidential salary to charities including the United Negro College Fund and the Boy and Girl Scouts.

According to Gaming Law, casinos have to stock enough cash to cover all the chips on the 'floor'.

About 10% of US households pay their bills in cash.

The Federal Reserve printed up an extra $50 billion in small bills just in case people started hoarding money prior to the year 2000. Since nowhere near that much cash was needed, and there was a long-term storage problem, most of that money was recycled.

Martha Washington is the only woman to have been featured as the primary portrait on US paper currency (see below). Her image first appeared on the front of the $1 Silver Certificate in 1886, and she also appears alongside her husband George Washington on the back of the 1896 series.

A US one dollar bill isn't really paper at all: it is made from a blend of 75% cotton and 25% linen, which makes it far more durable and harder to counterfeit than ordinary paper.

The highest denomination of US currency ever printed was the $100,000 gold certificate, bearing a portrait of Woodrow Wilson. Issued during the Great Depression in 1934, it was never given to the public and was used only to move balances between Federal Reserve banks. It remains illegal for a private individual to own one.

The world's first cash machine opened at a Barclays branch in Enfield, north London, on 27 June 1967. There were no plastic cards; customers inserted a special paper voucher to withdraw a single £10 note, and the first withdrawal was made by On the Buses actor Reg Varney.

Cash wears out at very different rates depending on how often it changes hands. A well-used $1 bill lasts only around 21 months, whereas a $100 bill, handled far less, can survive for more than seven years.

The largest single banknote ever put into circulation was the Philippines' 100,000-peso note, created in 1998 to mark a century of independence from Spain.