On this day in 2009, the first transaction ever broadcast over the Bitcoin network was sent by Satoshi Nakamoto to Hal Finney in block 170. Satoshi sent 10 BTC to Hal, who was the first person besides Satoshi to run the Bitcoin software. This transaction proved that peer-to-peer electronic cash transfers worked as described in the whitepaper. Hal Finney, a renowned cryptographer and cypherpunk, had replied "Running bitcoin" on Twitter just the day before.
View the genesis transaction
here.