The lane marked "First Class" is indeed at the far left side of the sea of humanity waiting at the D concourse security screening.

As I walked toward the line on Monday morning at 7 am, TSA guy unhooks the rope and lets 75 or so people from the general line into the elite/first line just as I am approaching. D'oh!

When I get to the ID check line, he sees my gold 1P card and sends me to the crew-only line. ^