Height of Wrapper

Alright I am currently working on creating my first theme and need some help!

I want have a different color (maybe an image, after I figure all this stuff out) for the #wrapper. The problem is that if I don’t enter a height it only covers the #header. I tried changing the height to a random number and of course it shows it to that height.

Problem…I don’t want it to be a certain height…I want it to cover the content of the page.

Is there a code to enter to my style.css to make that happen??

Thanks,
Diane