I'm at PDX right now and the sign is still posted at least (the one that shows each different airline allowed to use the elite security line, and the cards/membership levels required for each airline). As far as I remember, Southwest was not listed.

For UA, There was a 1P and two 1K cards shown next to the United logo. I assume one of the 1K cards is a GS card? They're overlapping so they just looked like two slightly different 1K cards on the sign.

There was no line at security so I didn't get to try just getting by without flashing an elite card as a test. Oddly, the ID checker 1) required me to remove my drivers' license from the transparent sleeve which almost never happens, and 2) highlighted and initialed stuff on my DM Card!