According to this article from yahoo! 49 out of 50 states have at least a dusting of snow or more in some part of them. The hold out is Hawaii where its 13,800-foot Mauna Kea volcano that usually sees snow in the higher elevations remained snow free as of present. Cilmatologists cannot say if 50/50 or even 49/50 states with snow cover has ever even happened as such an event is so unlikely that records haven't been kept.

More information here:

http://news.yahoo.com/s/ap/20100213/ap_on_re_us/us_united_states_of_snow

This has been a wild winter!