Dosch was born on June 17, 1841, in Kastel, Germany and was one of seven children born to Colonel John B. Dosch and his wife Anna (née Busch), a sister of Adolphus Busch. Dosch attended the Gewerbeschule für Handel und Industrie, graduating in April 1857. Dosch then apprenticed at a large oil importing house in Mainz until January 1860. On January 17, Dosch sailed for America and made his way to St. Louis, Missouri, where he worked as a bookkeeper until the start of the Civil War.
