Where it came from
On 30 August 2011 a forum account named piuk opened a thread on Bitcointalk under the title "Blockchain.info - Bitcoin Block explorer & Currency Statistics". The pitch was two things at once: a public web page for looking up any Bitcoin address, transaction or block, and a browser wallet where, in the thread's words, "You retain 100% control over your bitcoin private keys."
The explorer is the part that mattered first. In 2011 there was no other convenient way to see what the chain actually contained without running software yourself, and blockchain.info became the address bar of Bitcoin for people who had no node. Journalists used it, developers used it, and so did anyone tracing stolen coins. Its own about page in May 2014 read: "Blockchain.info is Bitcoin's most popular bitcoin wallet and block explorer. As of January 2014 the site has over 1.1 million registered users and 200 million page views per month."
The tradeoff it shipped
The wallet encrypted keys in the browser rather than on the server, which is a real distinction from an exchange account. It is not the same as holding keys offline. A wallet whose code arrives fresh from a web server on every visit trusts that server every single time, and that has always been the honest objection to the design.
What it is now
The company describes itself on its own about page as having built "the original Blockchain Explorer" and an API on top of it, and now claims more than 95 million wallets created and over $1.1 trillion moved. It is no longer one site. Its terms of service allocate services across a group of separate companies, including Blue Cube (Malta) Limited for most of the world, Blockchain.com, Inc. for United States residents, and entities registered in the British Virgin Islands and the Cayman Islands for rewards and staking products. Its United Kingdom company, Blockchain.com Operations (UK) Limited, number 15126764, was incorporated on 10 September 2023 under the earlier name BC Operations Limited. Its about page names Peter Smith as chief executive, co-founder and executive chairman, and Nic Cary as vice chairman and co-founder.