They are quite a sight, aren't they?
I love seeing them too, though I haven't seen one for a while. They like dead trees as they eat insects, and carpenter ants and other bugs live in dead trees. You probably saw two of them together a while ago as it was breeding season, and now it's the off season, so they're more likely to be solitary at this time of year, though they do form long term pair bonds.
Their sound is pretty distinctive, though the Northern Flicker has a similar call. So you may have them around too, and if so, try and see them too. They're really pretty as well, and they (as well as Pileated Woodpeckers in the area) may actually show up at a bird feeder if you put out suet.