The combined Union Pacific-Central Pacific line became known as the First Transcontinental Railroad and later the Overland Route. The line was constructed primarily by Irish labor who had learned their craft during the recent Civil War.
What is the source what is it referring to
They declared war on May 13, 1846!
(C)
It was part of an Act that was passed, that provided Prosecution of a war that was already between U.S. and Mexico.
I can confirm the answer is A. federalism