What is Frontier (July 2015)?

Frontier was the name given to the first version of the Ethereum mainnet, which launched in July of 2015 and made use of a Proof-of-Work (PoW) consensus mechanism. Frontier was a fairly bare-bones structure that got the network off the ground. It provided a command line interface (CLI) to mine ether (ETH) and upload and execute smart contracts — nothing more. The initial launch of Frontier and the Ethereum network took place between the initial founding of Ethereum in 2013 and its subsequent mainnet launch in 2015.