In the 1840s, why did so many irish people move to the united states?

they were suffering religious persecution in ireland.
there was a war going on at that time in ireland.
ireland’s potato crop failed due to a disease.
ireland was very overpopulated at that time.

i do not know if this question has options, but a main impact of the federal reserve act of 1913, which created the federal reserve bank, was the international use of the u.s. dollar, which soon became the world's leading currency - particularly during world war i, since many nations around the world asked the united states for money.