What is the value of a 1957 US silver dollar?

The US didn't mint any $1 silver coins after 1935.

If you have a coin with the Liberty Bell on the back, check the denomination under it - it's a HALF dollar.

If you have a paper bill with a blue seal and serial numbers, it's called a silver certificate rather than a "silver dollar".

In either case please check the Related Questions for more information.