How to add a class to a Drupal 7 region?

I am trying to add a .clearfix class to my footer region in a Drupal 7. Is there a way to do this?

I am currently using the following to print my footer region:

<?php print render($page['footer']); ?>

Which outputs:

<div class="region region-footer">
   <div id="block-1>....</div>
   <div id="block-2>....</div>
</div>