Idiot politicians catering to the clueless and unwashed.
All American Law stems from the original Constitution of the United States. It is considered the "supreme law of the land".
trial and error
English common law, someone called Blackwell (if I remember right), and a lot of politicians who get elected and then feel that they have to do something to justify their elections so they make up stuff often best left undone.
Or it comes from politicians trying to buy votes by appeasing every pressure group in their constituencies, so they pass a law on any subject three people will yell about.
The first law in most states is the "reception" statute, which makes the basic law of the state the English common law in the year 1607 in the reign of James II. Common law is the law made by judges, not by the legislature.
You want a law history lesson? Most law follows English common law. Louisiana follows a lot of French law (civil). California has codified all their laws. They got a number/code for everything. US has Federal court system and state court systems. Higher courts set precedence by their rulings.
FROM GREAT ENGLAND