I would call them to be sure as it might vary with the seasons
From their website: Tour Times: 9:30, 10:30, 11:30, 12:30, 1:30, 2:30, 3:30, 4:30 Please arrive 1/2 hour before tour you would like to take! Adults $27 Children 11-under $20 Although the maps information indicates hours are 9-4. Call them to avoid a problem.
I think the last tour is 4pm but I would call them and verify
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