BitShares was founded in 2014 by Dan Larimer, a cryptocurrency visionary and early adopter. He first started working with Bitcoin in 2009. But after some centralized exchanges started to shut down for no apparent reason, Larimer realized that a decentralized exchange is necessary. From this idea, BitShares was born.
As Larimer explained in this blog post, BitShares is, amongst other things, a software, network, ledger, community and most notably a decentralized peer-to-peer exchange. BitShares aims to remove the need to trust a centralized authority to oversee transactions and handle funds.
Dan Larimer has an extremely impressive resume, and has been the lead developer on both EOS and Steem, in addition to Bitshares.