It's not an official holiday - yet - but for many cryptocurrency enthusiasts "Bitcoin Pizza Day" is still special. Thursday marks the 15th anniversary of the first known use of cryptocurrency to buy real-world goods.

The 10,000 bitcoin that software developer Laszlo Hanyecz paid for two Papa John's pizzas delivered to his Florida home on May 22, 2010, were worth about $41 at the time. Today they're worth $1.1 billion, as bitcoin hits record high prices.

Several cryptocurrency companies are announcing promotions and other celebrations to mark Bitcoin Pizza Day. Bitget, a cryptocurrency exchange, announced that it's giving away pizzas to more than 2,000 people at gatherings held around the world.

Here's the backstory of Bitcoin Pizza Day:

The first bitcoin was created in early 2009 by the digital currency's still unknown creator, Satoshi Nakamoto. It started as a passion project for libertarian-minded computer nerds who wanted to create a digital payment system that didn't rely on a third party - like a government or financial institution - for transactions.

Hanyecz was an early enthusiast and became active on an early bitcoin internet message board, offering technical advice on how to "mine" bitcoin more effectively.

Central to bitcoin's technology is the process through which transactions are verified and then recorded on what's known as the blockchain. Computers connected to the bitcoin network race to solve complex mathematical calculations that verify the transactions, with the winner earning newly minted bitcoins as a reward in a process known as mining.

In the early days, enthusiasts could mine bitcoin through their home computers and Hanyecz accumulated thousands of the new digital asset. Nowadays, mining bitcoin has become a highly competitive field with multi-billion-dollar companies using specialized computers in entire data centers to acquire new bitcoins.

In the early days, no one quite knew what to do with the bitcoin they were mining. On May 18, 2010, Hanyecz tried an experiment and posted a message offering 10,000 bitcoins for pizza.

"I like things like onions, peppers, sausage, mushrooms, tomatoes, pepperoni, etc.. just standard stuff no weird fish topping or anything like that," Hanyecz wrote.

Three days later, Hanyecz wondered if he needed to up the price.

"So nobody wants to buy me pizza? Is the bitcoin amount I'm offering too low?" he wrote.

But the next day, Hanyecz said he'd successfully traded his bitcoin for pizza. Another bitcoin enthusiast from California had paid for the Papa John's pizza in exchange for the cryptocurrency, according to a book about bitcoin's early history, "Digital Gold."

"A great milestone reached," said another early bitcoin enthusiast on the message board congratulating Hanyecz.

It did not take long for bitcoin to take off after the first pizza deal. Bitcoin started getting more publicity and grew, thanks in part to the popularity of an online black-market site, Silk Road, which only accepted bitcoin.

By February 2014, with bitcoin trading at around $600, Hanyecz marveled at what the digital currency had become.

"I mean people can say I'm stupid, but it was a great deal at the time," Hanyecz wrote on the bitcoin message board. "I don't think anyone could have known it would take off like this."

Five years later, when bitcoin was trading as high as $11,000, Hanyecz reflected on what buying that first pizza meant for bitcoin.

"It made it real for some people, I mean it certainly did for me," Hanyecz said on the television show "60 minutes."

Hanyecz has largely stayed out of the public spotlight in recent years and efforts to contact him by The Associated Press were unsuccessful.

After many years of fits and starts, bitcoin now appears firmly entrenched in the mainstream financial system. While it hasn't taken off as a way to pay for everyday items like pizza, bitcoin has found popularity as a kind of "digital gold," or a way to store value.

Retirement accounts can buy bitcoin ETFs, more and more companies buy bitcoin as corporate treasuries, and President Donald Trump recently signed an executive order establishing a government reserve of bitcoin.

Bitcoin was trading at about $111,000 on Thursday morning -- a new record. That price gives it a market cap of more than $2 trillion, or about the same as Amazon.