Why is there a blue law prohibiting the sale of cars on Sundays in many states?

Question by BugsySkybone: Why is there a blue law prohibiting the sale of cars on Sundays in many states?
Could it be argued that this is unconstitutional, given the fact that "blue laws" are typically in place due to someone's religious preference and the fact that the sale of cars is a pretty secular activity?
OK, Small But Fierce, let me educate you a little. When I say "secular" I am using the Merriam Webster definition of the word, not your misunderstanding/lack of knowledge of the

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