What was the first US law to restrict immigration

On August 3, 1882, the forty-seventh United States Congress passed the Immigration Act of 1882. It is considered by many to be "first general immigration law" due to the fact that it created the guidelines of exclusion through the creation of "a new category of inadmissible aliens."

Explanation:

nothing certain is known about what happened, but it seems that the country declined gradually, perhaps due to bad government, or, more likely, due to a series of bad harvests, which resulted in widespread and recurrent famine.