US State Outlines

The best trove of data about the US comes from the US Census bureau in the form of the TIGER/Line shapefiles, which Cartographica will happily read.

The main entry point for TIGER data is: http://www.census.gov/cgi-bin/geo/shapefiles2010/main

For more information: 2010 Tiger Overview

For state outlines:

1. Go to the Tiger Shapefiles/2010 site
2. Select States (and Equivalents)
3. From the State and Equivalent (2010) menu, select "All states in one national file" and click Download
   This will result in a file named tl_2010_us_state10.zip on your hard drive 
4. Go to that file in the finder (you can click on it in the Safari Downloads window (or Popover in Safari 5 on Lion)
5. Double-click the file to decompress it (it is a zip file that contains the full shapefile data set) and the Finder will decompress it into usable form
6. Either use File > Import Vector Data... or drag the .shp file into a Cartographica document to import the data

To use with CartoMobile, drag all of the files from the folder into the CartoMobile section of the File Transfer area of the Apps tab