I should have added my current, non-working code. Please be gentle.
$committees = array(
'numberposts' => -1,
'post_type' => 'committee'
);
$query = new WP_Query($committees);
$location_array = array();
if( $query->have_posts() ):
while( $query->have_posts() ): $query->the_post();
$location_array[get_field('committee_name')] = get_field('committee_location');
endwhile;
wp_reset_query();
endif;