David Heinemeier Hansson (dhh) extracted Ruby on Rails from his work on Basecamp. He released the framework as open source in July of 2004, but didn't share the commit rights until February of 2005. Among the core team, he's infamous for his ruthless delegation, which is often executed as a request to "Please Do Investigate". He's a partner at 37signals and an opinionated blogger.

Jeremy Kemper (bitsweat) is a programmer at 37signals hailing from Pasadena, California. Hot on the heels of DHH, he has been the most active contributor to Rails. He's knee deep in pretty much all aspects of the framework and one of the top batters against new, incoming tickets.

Michael Koziarski (nzkoz) is a software consultant based in Wellington, New Zealand. After a successful stint as an enterprise Java developer, he switched to rails shortly after the first public release. He’s a contributor to The Rails Way and maintains a personal blog.

Rick Olson (technoweenie) blames Ruby on Rails for destroying his ASP.Net career. He's been using Rails actively since 2005 and is now working on making issue tracking enjoyable with Lighthouse. He's also released several open source projects, such as Mephisto, Beast, along with numerous plugins.

Pratik Naik (lifo) stumbled upon Rails back in 2006 while in search for a better web framework after 2 painful years with perl/mod_perl. He hasn't looked back since then. Currently located in London, he works full time on Rails applications and maintains a personal blog at http://m.onkey.org.

Josh Peek (joshp) has been working with almost all parts of Rails. A lot of work spent on performance and thread safety for Action Pack. He's the latest addition to the team.

Rails core members who are no longer active in the day-to-day stuff have been immortalized as core alumni.