All Electrical Systems are Dead!

I have a '96 4.3l Jimmy and long story short, the other day the battery went dead while driving it and the whole car quickly followed suit. At this point some minor electrical systems like the interior lights and power locks were still working, however the next day, I replaced the alternator, used a fresh battery and tested all the fuses near the driver side door, but nothing in the electrical system works.

The new battery reads 12.5V on a voltmeter and the connection to the alternator seems to be snug and also reads the same voltage as the battery.

There is also a green and black wire on a ring terminal that is sitting right behind the alternator not connected to anything. I do not recall disconnecting this while pulling the alternator and I have no idea what it is or where it goes.

Does anyone have any ideas? Any help would be greatly appreciated.

so you have no juice any point past the alt? did you see if that green wire had voltage? im not familiar with the 95+ models but im going to guess that may be your cookie right there. is it forked or a ring connector on it? could have just fallen off if forked.
it may supply power to somewhere very important!

try to look on autozone for a wiring diagram!

Its a ring, connector, and the wire doesn't have a lot of slack where it's at so it couldn't be far from the back of the alternator. Aside from connecting to the alternator mount (which wouldn't make much sense) I see nowhere for it to go. I think it might have been disconnected beforehand. If memory serves me right, it was at ground potential or at least minimal impedance to the battery ground terminal.