Seeing as how no one has posted a sufficient response yet, ill throw in my 2 sats. It all started when Satoshi Nakamoto sent out his vision of Bitcoin to the cryptography mailing list back in 2008. Then on Jan 3, 2009, Bitcoin was launched from the genesis block known as block 0. Satoshi Nakamoto himself mined the genesis block and this is where the very first 50 Bitcoin came from. He continued to mine and from that point forward its all history.

It is really interesting to read his email correspondence back in 2008, and I encourage anyone who is interested in this matter to check out: https://satoshi.nakamotoinstitute.org. It has a list of his early email correspondence and some other interesting tidbits.