@sdetweil - ahhh. I need to do this from the desktop:
pi@MagicMirrors:~ $ xrandr -q
Screen 0: minimum 320 x 200, current 2160 x 1920, maximum 7680 x 7680
HDMI-1 connected primary 1080x1920+0+0 left (normal left inverted right x axis y axis) 477mm x 268mm
1920x1080 60.00*+ 60.00 50.00 59.94
1680x1050 59.88
1280x1024 75.02 60.02
1440x900 59.90
1280x960 60.00
1280x720 60.00 60.00 50.00 59.94
1024x768 75.03 70.07 60.00
832x624 74.55
800x600 72.19 75.00 60.32 56.25
720x576 50.00 50.00 50.00
720x480 60.00 60.00 59.94 59.94 59.94
640x480 75.00 72.81 66.67 60.00 59.94 59.94
720x400 70.08
HDMI-2 connected 1080x1920+1080+0 right (normal left inverted right x axis y axis) 477mm x 268mm
1920x1080 60.00*+ 60.00 50.00 59.94
1680x1050 59.88
1280x1024 75.02 60.02
1440x900 59.90
1280x960 60.00
1280x720 60.00 60.00 50.00 59.94
1024x768 75.03 70.07 60.00
832x624 74.55
800x600 72.19 75.00 60.32 56.25
720x576 50.00 50.00 50.00
720x480 60.00 60.00 59.94 59.94 59.94
640x480 75.00 72.81 66.67 60.00 59.94 59.94
720x400 70.08
pi@MagicMirrors:~ $