William WRIGHT

I am looking for the birthplace of my 2nd great-grandfather, William WRIGHT. I think he was born on 25 Sept 1828 (d. 3 Aug 1903 in Ohio, USA) somewhere in the Dublin area. [In the 1930 USA Census, William's son, John T. Wright, indicates his father was from the "Irish Free State" (1922-1937) which existed long after William came to the US, but which leads credence to William's origin in Dublin.] William emigrated to the United States in 1840 (according to USA census records), but I haven't been able to identify the ship name or port. A handwritten family document, unsigned, but we believe from William's granddaughter, Ida May Wright (1890-1985), states , "Dad's [Ed: Ida's father and William's son, Robert (1856-1930)] father and mother came from Ireland but didn't know each other in Ireland met in Philadelphia Penn, married came to Ohio ... . William's spouse was Martha Fulton PAUL (20 Apr 1829 - 13 Oct 1918), my 2nd great-grand-mother, we think was from Londonderry, Darry County, Ireland. Martha also emigrated to the US in 1840 (again, no ship/port info). Any leads/help to identify Irish origins of William WRIGHT or Martha PAUL would be greatly appreciated.