Write SQL query to solve given problem: Among the customers from Chicago, Illinois, what is the highest quantity of products bought in a single order?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T1.Quantity FROM west_superstore AS T1 INNER JOIN east_superstore AS T2 ON T1.`Customer ID` = T2.`Customer ID` INNER JOIN central_superstore AS T3 ON T3.`Customer ID` = T2.`Customer ID` INNER JOIN south_superstore AS T4 ON T4.`Customer ID` = T3.`Customer ID` INNER JOIN people AS T5 ON T5.`Customer ID` = T4.`Customer ID` WHERE T5.City = 'Chicago' AND T5.State = 'Illinois' ORDER BY T1.Quantity DESC LIMIT 1