Twentyeleven Sidebar Height

I’m attempting to make the sidebar height (left side) extend from the banner to the footer vertically, so that the content visually appears the same as the main content area (right side). Currently, the sidebar has a brown background (the main content area is white), but only extends as far vertically as the widgets within in (a navigation bar and search function). I’ve spent a dozen hours with Firebug (using height: 100% and various background-color:) on all the relevant inherited styles and still can’t get it to function appropriately. Can someone explain what I am missing? Thank you!