Where it came from
Blockstream's own history page dates the company to 2014 and names Adam Back, Erik Svenson and Pieter Wuille "and others" as its founders. The public record agrees on the year: a Form D filed with the US Securities and Exchange Commission in October 2014 identifies the issuer as BlockStream Corp, previously 8425345 Canada Inc., a corporation whose jurisdiction of incorporation is recorded as Canada at the federal level and whose year of incorporation is given as 2014.
The founding pitch was sidechains, a way to move bitcoin onto a separate chain with different rules and back again, without changing Bitcoin itself. That idea produced Elements, released in June 2015, and then the Liquid Network in October 2018.
What it built
Blockstream's own product list separates consumer tools from what it calls community projects. On the consumer side there is the Blockstream App and Blockstream Jade, which the company describes as "a fully-open source hardware wallet for Bitcoin and Liquid". On the infrastructure side there is Core Lightning, an implementation of the Lightning protocol launched as c-lightning in December 2017 and renamed in March 2022, plus Elements, Simplicity and the Liquid Network. Blockstream Satellite, launched in August 2017, broadcasts the block chain from space so a node can stay in sync without an internet connection.
What it changed
Two things, mostly. Core Lightning made Lightning a multi-implementation network rather than one codebase, which matters because a protocol with one implementation is a protocol with one bug away from a bad day. And the company employed a number of the people doing protocol research and Bitcoin Core review work, which put a commercial payroll behind maintenance that had until then been unfunded.
Blockstream describes itself as distributed, with offices listed in the Cayman Islands, the Bay Area, Los Angeles, Montreal, Victoria, Lugano, Milan, Turin, Melbourne and Tokyo. Listing here is not endorsement.