Dergenagh () is a townland in County Tyrone, Northern Ireland. It is situated in the historic barony of Dungannon Lower and the civil parish of Killeeshil and covers an area of .
John Simpson, the maternal great-grandfather of Ulysses S. Grant, 18th president of the United States, was born and lived in Dergenagh until emigrating to the United States in 1760. His home, now the US Grant Ancestral Homestead, still stands and is now operated by Mid-Ulster District Council as a tourist attraction.Thompson, Joseph E., "American Policy and Northern Ireland: A Saga of Peacebuilding", Praeger (March 30, 2001), p. 2, and Howe, Stephen, "Ireland and Empire: Colonial Legacies in Irish History and Culture", Oxford University Press, USA (March 14, 2002), p. 273. Grant himself visited his ancestral home during his world tour in 1879, and shares a robust lineage of Ulster-Scots Presidents.
See also List of townlands of County Tyrone
References