I have the Nuvi 1490LMT and I downloaded "City Navigator North America NT 2013.30,US & Canada - Map+P, Oct 12". I have a 16gig SD card in my device with over 14gig available. When I try to download to my device, the full US and Canada is available to download, as are all the regions except "Lower 49 States". Are those regions more detailed than the full US and Canada? Why would the full one be available but not Lower 49?