All County - Ireland & for Woocommerce
$fields['billing']['billing_state']['options'] = array(
'carlow' => 'Carlow',
'cavan' => 'Cavan',
'clare' => 'Clare',
'cork' => 'Cork',
'donegal' => 'Donegal',
'dublin' => 'Dublin',
'galway' => 'Galway',
'kerry' => 'Kerry',
'kildare' => 'Kildare',
'kilkenny' => 'Kilkenny',
'laois' => 'Laois',
'leitrim' => 'Leitrim',
'limerick' => 'Limerick',
'longford' => 'Longford',
'louth' => 'Louth',
'mayo' => 'Mayo',
'meath' => 'Meath',
'monaghan' => 'Monaghan',
'offaly' => 'Offaly',
'roscommon' => 'Roscommon',
'sligo' => 'Sligo',
'tipperary' => 'Tipperary',
'waterford' => 'Waterford',
'westmeath' => 'Westmeath',
'wexford' => 'Wexford',
'wicklow' => 'Wicklow'
);
<select name="county" id="county">
<option value="Carlow">Carlow</option>
<option value="Cavan">Cavan</option>
<option value="Clare">Clare</option>
<option value="Cork">Cork</option>
<option value="Donegal">Donegal</option>
<option value="Dublin" selected="selected">Dublin</option>
<option value="Galway">Galway</option>
<option value="Kerry">Kerry</option>
<option value="Kildare">Kildare</option>
<option value="Kilkenny">Kilkenny</option>
<option value="Laois">Laois</option>
<option value="Leitrim">Leitrim</option>
<option value="Limerick">Limerick</option>
<option value="Longford">Longford</option>
<option value="Louth">Louth</option>
<option value="Mayo">Mayo</option>
<option value="Meath">Meath</option>
<option value="Monaghan">Monaghan</option>
<option value="Offaly">Offaly</option>
<option value="Roscommon">Roscommon</option>
<option value="Sligo">Sligo</option>
<option value="Tipperary">Tipperary</option>
<option value="Waterford">Waterford</option>
<option value="Westmeath">Westmeath</option>
<option value="Wexford">Wexford</option>
<option value="Wicklow">Wicklow</option>
</select>