I want to combine several topo maps

[rsscoggins]

All

I want to combine a Texas, OK, and AR topo maps into one - I don't even know where to begin...

[Boyd]

What kind of GPS do you have? The technique is different on the Oregon/Colorado/Dakota.

[rsscoggins]

I have a Garmin 60Cx. 

[Boyd]

In that case, install all the maps into mapsource. Now use the dropdown menu to choose the TX map and select all of it with the selection tool. Next you would choose the OK map from the menu and select all of it as well. Continue until you have selected all of your maps. In the pane on the left you should see them all listed.

Now use the transfer menu to send everything to your GPS. On the GPS you can choose which maps you want to display. When combining maps from different sources, you may be some oddities in areas where they overlap if you make them all active.

[Jimbob]

In the left pane of mapsource it will tell you how much space your combined maps will require after you select them. Make sure you have enough space left on your sd card.

[maps4gps]

There should be no problems with the three mapsets working as one on the GPSr.   The quads have consistent ids.  Where the same quad(s) occurs in different mapsets, MapSource will list each in the list box on the left; however, it only uses one in building the gmapsupp.img file.  I did not test to see if which one was consistent (i.e. like from the first or last State selected) or random.
What does happen is that the quad is assigned to one of the States and if you decide to hide/disable that State the quad(s) will be hide/disable even if the other State(s) are displayed.