While Chester’s father, Reverend William Arthur, was foreign born, he had immigrated to the United States from northern Ireland when he was 18 and had become a Baptist minister.
Northern Ireland did not exist when Chester Arthur's father was born in County Antrim.
William Arthur graduated from Belfast College before coming to America. He studied law before becoming a preacher.
I did not find any material on when/if Rev William Arthur became an American citizen.
William Arthur emigrated from Ireland to Canada, not the United States. William Arthur migrated to the Province of Lower Canada on date uncertain, circa 1819-1820. Lower Canada would now be in the Province of Quebec. Chester Arthur's mother Malvina met his father while William Arthur was living in Canada.
William Arthur was naturalized 31 August 1843. Chester Arthur born 1829.
