On Import, where is county field?
The issue is almost certainly that the "County" field is not enabled by default, which suppresses it in the import dialog.

Go to Administer menu > Localization > Address Settings, and under "Address Editing", see if the "County" box is checked.  If not, check it.  Restart your import and the field should appear.

I also confirmed your report that County appears even if disabled as a field for related contacts.  That's a bug, though a very low priority one!