The bulb is fine.
I'm getting 0 volts to the light.
Its the driver's side light on the body (not the trunk).
The turn signal works.

I've followed the harness as far as where it tangles up with the rest of the rear lights. I just wanted to get some quick input before I had to open the harness and follow it all the way up to the switch.

Is there 1 switch for all 5 lights? or separate switches for each? Where does the harness actually go (all the way to the front)?

 

Yes, all the way to the front. Check fuses.

 

Chances are your sub-harness connector is corroded, That's what happened to mine (Sheriff Barney Fife politely informed me when the light didn't work)