The National Data Buoy Center [NDBC], part of the NOAA, is a good source for wave height information. Data from several hundred buoys (not all theirs) is accessible on their website, often with historical records. The highest waves ever recorded by the NDBC buoys were in the North Pacific, near the Aleutian Islands, and had an H_s of 18m. A rogue wave in that storm could have reached a staggering 48m in height. The location is no accident. While 100-foot waves in the North Atlantic are rare enough that it took a "Perfect Storm" to create them, David Gilhousen, a metereologist with the NDBC, says that in the North Pacific "sea waves of that magnitude are something you would see every other year -- maybe every year" [Chui2000]. Not the best place to build a seastead.