How long did it take the United States to become an optimal currency area?

The US monetary union began with the ratification of the Constitution in 1788. It has remained intact, with the exception of the Civil War years, ever since. And the United States has grown and prospered during that time. But it does not follow that the United States has grown and prospered because it has had a monetary union. The benefits of the monetary union – the relative ease with which interregional movements of capital, labor, and final products could take place – are evident. The costs of the monetary union, that I intend to focus upon here, are less evident, but nonetheless important.