I know it's a big county, but this Gallagher could be a relative of our Gallagher:
Bridget Gallagher was my husband's great-grandmother. She was born in 1838, exact Irish location not yet found, She married Patrick ("Ned") McCabe; they lived at Straworter, Ardara, Co. Donegal, where she died in 1865. As her husband also died that year at the Fever Hospital, Glenties, Co. Donegal, it is possible that she died of fever also. They had 4 children together. I am certain only of the names of the youngest two: Susan McCabe (died 1907) at the birthplace/Straworter, and Joseph Patrick McCabe who emigrated to the US in 1880. At first JP McCabe worked in the Pennsylvania coal mines, but he eventually became a district manager for the Metropolitan Life Insurance Co. He died in 1919 @Shenandoah PA of pneumonia resulting from the Great Flu Pandemic of 1918. He fathered seven children. His youngest son, also Joseph Patrick McCabe, was the father of my husband.
Posting this just because "you never know." It's a very small world; smaller all the time.