Geisinger was born in Maryland in 1790 and was appointed midshipman in the United States Navy, on 15 November 1809. During the War of 1812, he was on board the sloop-of-war . On 21 September 1814, an eight-gun merchant brig, the "Atalanta", ran afoul of "Wasp", and was captured. Deemed too valuable to destroy, "Atalanta" was placed under the command of Midshipman Geisinger and was sent home to the United States. Geisinger arrived at Savannah, Georgia, safely on 4 November 1814. His good fortune was to escape from the fate of the "Wasp", which was lost with all on board. He was promoted to lieutenant on 9 December 1814.