How common is power rear windows in Wagons?

slant6/4speed said
I was looking at my 66 Valiant wagon and realized that I have not seen other A-body wagons with electric rear windows. Was it a unpopular option?

I don't think so. They were more popular on B and C body wagons, particularly with a rear facing 3rd row seat. Most of the times that I have seen a power tailgate window it was on a VH or a LH wagon. That's not to say I haven't seen them on the the VL and LL lines. To take a SWAG at it, VH/LH 40%, VL/LL 20%. In fact the last one I saw in a salvage yard was a '63 VL, 170, 3 spd, htr/def, radio, and PTW.

slant6/4speed said
What years was it offered?

I have seen them on 62-66 wagons.