Because of the St. Augustine City rules.
So that they can go home and watch Wheel Of Fortune.
We vacation there every year at Christmas and have run into that question ourselves. The sites stay open later so don't get caught like us and miss the last trolley and end up walking back to your car. It's a very long walk.
Maybe because it's hard to see when it's darker outside since there aren't a lot of street lights?
You can call them. Maybe the sites close just as early?
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