Who invented the US 2 dollar bill?

Answer 1

Banknotes aren't "invented". That refers to creating technology.

The denomination was introduced in 1862 as part of the first set of federally issued bills. It makes sense as part of a decimal currency system because 1, 2, and 5 are factors of 10; i.e. denominations should be $1, $2, $5; then $10, $20, $50, and so on.

Unfortunately during the late 19th century the $2 bill was commonly used to make bets at racetracks and pay for sexual services in those pre-inflation days. As a result it became associated with what the general public considered to be "unsavory" practices and its use declined significantly. Today $2 bills make up only about 1% of all bills in circulation, but even so that still amounts to hundreds of millions of them. Modern ones aren't rare or valuable, just uncommon, so feel free to ask for them at your bank and spend them.