Remove all Dashboard Widgets and make Dashboard a single colum display.

gistfile1.phtml

function myplugin_admin_custom_ui() {
        if ( is_admin() ) {

	      // Remove All Dashboard Widgets.
	      remove_meta_box( 'dashboard_activity', 'dashboard', 'normal' );
	      remove_meta_box( 'dashboard_right_now', 'dashboard', 'normal' );  
	      remove_meta_box( 'dashboard_recent_comments', 'dashboard', 'normal' ); 
	      remove_meta_box( 'dashboard_incoming_links', 'dashboard', 'normal' );  
	      remove_meta_box( 'dashboard_plugins', 'dashboard', 'normal' );   
	      remove_meta_box( 'dashboard_quick_press', 'dashboard', 'side' );  
	      remove_meta_box( 'dashboard_recent_drafts', 'dashboard', 'side' );  
	      remove_meta_box( 'dashboard_primary', 'dashboard', 'side' );
	      remove_meta_box( 'dashboard_secondary', 'dashboard', 'side' );
	      remove_meta_box( 'rg_forms_dashboard', 'dashboard', 'core' ); // Remove Gravity Forms Dashboard Widget        
	      
	      // Condense Dashboard to a single column.
	      function myplugin_single_screen_columns( $columns ) {
		    $columns['dashboard'] = 1;
		    return $columns;
	      }
	      add_filter( 'screen_layout_columns', 'myplugin_single_screen_columns' );

	      function myplugin_single_screen_dashboard() {
		    return 1;
	      }
	      add_filter( 'get_user_option_screen_layout_dashboard', 'myplugin_single_screen_dashboard' );
 
        }
}
add_action( 'admin_init', 'myplugin_admin_custom_ui' );