I have added additional country regions to Magento's directory_country_region and directory_country_region_name tables. My understanding is that when a country is selected for which regions are stored then a drop down will automatically be added to the "create account" form in the cart when that country is selected. The drop down does appear for countries that are already listed in the regions tables. However, if the country for which I have just added new regions is selected then there is just a plain text input to type the region name/code into.
I have added the country to the "State is required for" field in config. The new region IDs dont start exactly where the existing ones finish up. The existing ones go as fat as approx 480 and I've started at 600 - does that matter?
Thanks a lot