In the US, the creator of a work (working as an independent artist, not creating the art as an employee) owns the copyright to the work when it is created. If you are working as an employee in creating the work, the employer owns the copyright. The copyright can only be transferred in writing to someone else. In other words, you would have to sign something that states you are transferring all rights (the copyright) to that person. The ownership of the original work is separate from the copyright. A person buying the original artwork is not buying the copyright to reproduce it, unless those rights are specified in writing and signed by the artist.

You can register a collection of your unpublished work (such as Alice Flynn's collective work of 2001) in one batch for $30. Work registered after it is published is registered for $30 for each published work. It is more affordable to register new work in batches as it is created, like every month or so, before it is published.

You can also simply add the copyright notice to the work © your name, date and not bother to register it. If your work is ever ripped off, though, having it registered makes it much easier to defend the proof of ownership.

You can get the information online here:
http://www.gag.org/about/us_copyright.html
Guild copyright info.

You can register your work here as well as read the Library of Congress copyright FAQ: http://lcweb.loc.gov/copyright/
Library of Congress copyright site.

Realize that when you create a work, you can license usage of the work in different way, like first North American publication rights, for example. Each division of the rights to reproduce the work has a value, and an artist should license only that which the buyer needs and no more.

Alice Flynn