If you purchase a GPS from Sendero with the 8GB card, we load the maps for you on 3 folders. Maps1West has 37 maps, Maps2East has 29 maps and Maps3 Off Shore has 4 maps for Alaska, Hawaii, Puerto Rico and Guam. You could do the same sort of thing on 2 4GB cards. You can in fact load up to 75 maps in one folder in case you want to create a route from coast to coast. If you do this, you shouldn't however load all the Points of Interest files as this will use up too much memory to have them all open at once. Load the Core POI files and not the Bonus POI files and you will be fine. For 99.9% of situations, splitting the country in half should be more than enough. Here is the text from the ReadMe file that covers this topic. Mike * When the GPS program loads, it opens every POI file in the active folder. By having an image of each POI file in memory, searches and Look-Around functions are grately sped up. Although you can load up to 75 POI files from one folder and 75 maps on the mPower or PK, be aware that this is using up a lot of memory. We recommend that you limit the number of POI files to those you actively need. The maximum on the Classic is 12 maps and 30 POI files. There are over 120 POI files for the U.S. If you wish to calculate a route across the U.S., at most load the Core POI files so you have less than 75 POI files. We recommend splitting the total number of U.S. maps into no fewer than 2 or 3 folders.