On August 11, 1862, twenty-eight-year-old Dr. Frank J. Mattimore left his medical practice in Albany to become the assistant surgeon for the 18th New York. Soon after he joined the regiment, the Battle of Crampton's Gap was fought on September 14, 1862. With a large amount of casualties and few doctors, Mattimore was detached from the 18th for a time to tend to the wounded in hospitals in and around Burkittsville, Maryland. He eventually returned to the regiment on October 20, 1862.
Mattimore started a diary in a small leatherbound planner
the same day he entered the military which chronicled his various duties as a surgeon. The original is part of the artificats collection at the New York State Military Museum and Veterans Research Center in Saratoga Springs, New York.
Mattimore eventually contracted his own disease from the war, and shortly after he returned home he died on October 11, 1863.