Exhibit 21 List of Subsidiaries of State Auto Financial Corporation State Auto Property and Casualty Insurance Company, a South Carolina corporation State Auto National Insurance Company, an Ohio corporation Stateco Financial Services, Inc., an Ohio corporation Strategic Insurance Software, Inc., an Ohio corporation Milbank Insurance Company, a South Dakota corporation Farmers Casualty Insurance Company, an Iowa corporation Mid-Plains Insurance Company, an Iowa corporation State Auto Insurance Company, an Ohio corporation 518 Property Management and Leasing, LLC, an Ohio limited liability company