To review: DIPPAM (Documenting Ireland: People, Parliament, and Migration) is an online virtual archive of documents and sources relating to the history of Ireland, and its migration experience from the late 18th to the 20th centuries. In this series I am focusing on one part of DIPPAM, the Irish Emigration Database (IED).
The writing of letters was an important way for families to keep in touch when they lived on opposite sides of the Atlantic ocean. Those who were literate could avail of the opportunity and those who were illiterate might engage the services of someone who could read and write. The IED contains transcriptions of hundreds of such trans-Atlantic letters.
When doing research on Irish immigrants, one might presume that if their ancestors were from a low socio-economic status, then they could not write and this might not be an avenue of research worth exploring. However, due to chain migration in Ireland, and Irish people from the same part of Ireland settling in the same part of the U.S., information in such letters can often go beyond the direct family members.
For example, this letter was written by William Heatley to his sister, Mary, in 1851. William was living in Wexford Landing, Iowa, and wrote to his sister telling all about setting up in the area. In passing, he twice mentions a Fr. Hore, presumably a Catholic priest. Further research shows that Fr. Hore lead a substantial delegation of Catholics from Wexford, Ireland to America in the early 1850s. Many of them traveled on the Ticonderoga to New Orleans. They then sailed up the Mississippi until they found their new land in Allamakee county, Iowa. A transcribed listing of passengers shows a number of Heatleys in the traveling party, along with other people mentioned in the letter, such as Christina (presumably Christine Heatley on the passenger listing), Charles Redmond, and Mary Fennell.
This one letter, tied in with local history research in Iowa and passenger list information from the port of New Orleans, instantly opens up a broad range of research possibilities for both descendants of the letter writer and those who settled in the new Wexford colony.
 Hancock, Ellery M. Past and Present of Allamakee County, Iowa. Chicago: SJ Clarke Publishing. 1913. p.266.
 Murphy, Hillary. From Wexford Ireland to Wexford Iowa. Irish Family History. 1987. Vol. 3. Extracts available online at http://www.celticcousins.net/irishiniowa/wexfordia.htm: accessed 19 August 2014.
 Rees, Jim. A Farewell to Famine. Arklow: Arklow Enterprise Center. 1994. Extracts available online at http://www.celticcousins.net/irishiniowa/wexfordia.htm: accessed 19 August 2014.