The way I would organise this (and I have done this in the past) would be to have a post type for Work Sites, and a hierarchical taxonomy for Locations.
Then what you would do is add States as the top-level of the Locations taxonomy, and then add Cities as children of the State locations. Then you can assign a Work Site to a City and State.
Normally when you do this, if you attempt to view a State, rather than seeing a list of Cities you’ll see a list of Work Sites in that State. Which is not what you want. So what we need to do is modify the archive template for Locations to list subcategories instead of work sites.
So you’ll need to create a taxonomy-location.phpto use as the template when viewing States and Cities. Normally this template will have something like this in it:
<?php while ( have_posts() ) : the_post(); ?>
// Work Site template here.
<?php endwhile; ?>
This will list the Work sites in that Location. We need to change this to only list Work Sites if there are no subcategories for the current Location, otherwise list the subcategories:
// Get subcategories of current location.
$current_location = get_queried_object();
$sub_locations = get_terms( [
'taxonomy' => $current_location->taxonomy,
'parent' => $current_location->term_id,
] );
// If there are subcategories for the current Location...
if ( ! empty( $sub_locations ) ) :
// ...loop through and display them.
foreach( $sub_locations as $location ) :
// Location template here.
echo $location->name; // Location name;
echo $location->description; // Location description.
echo get_term_link( $location ); // Location URL.
endforeach;
// Otherwise...
else :
// ...list Work Sites for the current location.
while ( have_posts() ) : the_post();
// Work Site template here.
endwhile;
endif;
This method is flexible and will allow you have as many levels of Locations that you want, and only the lowest level will display the Work Sites.