Do we have free trade between the 50 states? Yes or no?
Not really, state laws impede to some extent the control by the International corporations and they interfere with the market all over the place. That is an important step towards free trade. But it doesn’t remove the other state involvements with its economy which stop progress toward free trade.
There are still big impediments to free trade between the states including the market controls I referenced earlier.
It was clearly the goal of the Founders to prevent states from imposing the biggest impediment to free trade. That is in the Constitution.
The Progressive Era produced all manner of state and federal regulations.