Some time in the past, before the ice age, most of western North
America (and probably the whole world) was accurately mapped by
a technologically advanced people. Who these people were and
what technology they used is lost to us, but their maps remain
as evidence that they did indeed accomplish the task. These
ancient source maps were used by mapmakers in the 1600 to 1700s
to fill in the vast unknown areas on the western side of North
America. The recent mapmakers had no idea what was there, nor
did anyone else, but they had source maps that showed the area
as an island and they used them to fill in the gaps. When were
these source map made? They had to be made before the end of the
ice age, because at the end of the ice age, the great ice dam
holding back water in a huge lake finally gave way and the Grand
Canyon was carved in just a few weeks. The Grand Canyon does not
appear on any maps of California as an island that I have found,
and is certainly not on the map used for this study, the
Vingboons map of