Bartholomew Dempsey was born in County Carlow, Ireland in 1833. He came to America aboard the Colonist in October 1851 and moved to Dehart St. in Morristown. In 1861, he enlisted with the 7th NJ infantry. He fought in the Peninsular Campaign, Chancellorsville and Gettysburg, being promoted to the rank of corporal in February 1864.

He was captured in the siege of Petersburg in June of 1864. He was first sent to Libby Prison in Richmond before being transferred to Andersonville. He survived the harsh conditions of the Andersonville prison, and was sent to Annapolis in 1865 at the end of the Civil War.

After the war, he married Catherine Jane Clifford in 1870 and they had four children. He was a painter by trade, and also became one of the first Morristown Marshalls in 1871. He held this position for a year.

He died of tuberculosis on March 20, 1879 at the age of 46, and is buried in Holy Rood Cemetery in Morristown, NJ.