Hello Graeme,
My name is Maria Mastin and I'm researching the COGAN family. This Cogan family immigrated from Sligo county, Ireland to the United States. They settled in Western Ohio in Auglaize county. The earliest Cogan I have found is John Cogan who was born about 1795 in Sligo, Ireland, married Mary Sheridan. Their son, Patrick Cogan married Sarah Monaghan. She was born May 1820 in probably Sligo Ireland and died Nov 12, 1903 in Auglaize county, Ohio. Patrick Cogan was born March 1822 in Sligo county, Ireland and died Jan 28, 1901 in Auglaize county, Ohio. In the 1880 census record, there lists with this couple: Anna Monaghan born about 1872 and James Monaghan born 1869.
Do you recognize any of these people? I think it's probably the same family as yours.
Please e-mail me at your convenience so that we can discuss these families.
Thank you. Maria Mastin