I just looked at one of the new screen shots and the Great Lakes is one big lake. What's up with that?

Perhaps that version of the map isn't large enough to allow that much detail.

I assume you are referring to this screenshot?

http://www.civfanatics.com/gallery/files/4/9/4/4/0/north_america.jpg

At least it makes it easier for ships to sail all the way down to the Midwest area. However, if you look at this image (http://www.civfanatics.com/gallery/showimage.php?i=1885&c=31), it appears that there will also be a Huge map for the entire Western hemisphere, so perhaps this will have a more defined Great Lakes region. You could try asking TheMystic too.

I was just excited to see that you'd be able to sail into the Great Lakes! This will make it more historically accurate since many settlements were along the Great Lakes and St. Lawrence River. Plus it opens up the Midwest to easier colonization.

Isn't the answer obvious? Each map called 'America' is a random ly gernerated map that has two large body masses connected by a thin strip of land. So there will ALWAYS be a lake in the map, but it'll be different each time!