Write SQL query to solve given problem: Which city in West North Central has the highest number of customers over the age of 60?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T2.city FROM client AS T1 INNER JOIN district AS T2 ON T1.district_id = T2.district_id WHERE T2.division = 'West North Central' AND T1.age > 60 GROUP BY T2.city ORDER BY COUNT(T2.city) DESC LIMIT 1