Here's the flexy way to do it. Of course, it's not supported by IE8, as the user needed 7 years ago. Depending on what you need to support, some of these can be done away with.
Still, it would be nice if there was a way to do this without an outer container, just have the text align itself within it's own self.
#header {
-webkit-box-align: end;
-webkit-align-items: flex-end;
-ms-flex-align: end;
align-items: flex-end;
display: -webkit-box;
display: -webkit-flex;
display: -ms-flexbox;
display: flex;
height: 150px;
}