Remove Sidebar when it contains no blocks

Short answer: remove the following lines in sites/all/themes/celadon/css/celadon-style.css:

#main-group {
  width: 656px;
}

and

.content-group-inner {
  width: 646px;
}

More appropriate answer: A considerable overhaul. The aforementioned answer doesn't address the #main-wrapper background:

#main-wrapper {
background:url("../images/container.png") repeat-y scroll center top transparent;
}

which includes the background for the sidebar region in question. Therefore, the main wrapper styling and sidebar styling would also have to be revised to maintain design integrity - which in turn presents additional issues, and creates more work.

For future reference in case anyone else runs into this issue this is all I had to change:

#main-wrapper {
  background: url(../images/container-2.png) repeat-y top center;
}
.content-group-inner {
  width: 946px;
}

I used this in a view and simply added the view id found in the HTML before the above CSS id/class, gave me one big column which is what I was looking for.