Please note that the layers in the Illustrator files are in a specific order so 
they will display correctly. Altering the layer orders may cause some features 
to "disapear". The files were created using Illustrator 9 on a Macintosh so earlier 
file versions (6,8) may have lost some formatting when converted. The format /symbols 
of these maps are not standard USGS and are for preliminary purposes only.