History of Bitcoin
Bitcoin is a cryptocurrency, a form of money that uses cryptography to control its creation and management, rather than relying on central authorities. However, not all of the technologies and concepts that make up bitcoin are new; the presumed pseudonymous Satoshi Nakamoto (the creator of bitcoin, see below) integrated many existing ideas from the cypherpunk community when creating bitcoin.
Pre-history
Prior to the release of bitcoin there were a number of digital cash technologies starting with the issuer based ecash protocols of David Chaum
and Stefan Brands. Adam Back developed hashcash, a proof-of-work scheme for spam control. The first proposals for distributed digital scarcity based cryptocurrencies were Wei Dai's b-money and Nick Szabo's bit gold. Hal Finney developed RPOW. Bit gold, b-money and RPOW all used hashcash as their proof-of-work algorithm.
Independently and at around the same time, Wei Dai proposed b-money and Nick Szabo proposed bit gold. Subsequently, Hal Finney implemented and deployed RPOW a reusable form of hashcash based on IBM secure TPM hardware and remote attestation (centralized but with no issuer inflation risk).