Below the steering column, to the left, there are two switches. The one on the left will say "cargo". That is the toggle for the cargo light to stay on. and if you accidentally turn it on and leave it on, it will not kill your battery because it goes off automatically after 15 minutes or so.
Interior drivers side cargo light.psd
The tailgate light, that also goes on with this switch. You can also hit the "unlock" button on your fob to activate it for 15 seconds to unload the last couple items.