Jakob Leonhard arrived from Lübeck at the port of Oranienbaum on 15 September 1766 aboard a ship under the command of Skipper Franz Nikolaus Schröder.
Jakob Leonhard, a farmer, and his wife Sophia are recorded on an appendix to the 1767 census of Beauregard in Household No. 2.
Widow Sophia Leonhard and her son Johann Martin are recorded on the 1798 census of Zug in Household No. Zr27.
The 1767 census records that Jakob Leonhard came from the German village of Leer.
- Mai, Brent Alan. 1798 Census of the German Colonies along the Volga: Economy, Population, and Agriculture (Lincoln, NE: American Historical Society of Germans from Russia, 1999): Zr27.
- Pleve, Igor. Einwanderung in das Wolgagebiet, 1764-1767 Band 1 (Göttingen: Göttinger Arbeitskreis, 1999): 195.
- Pleve, Igor. Lists of Colonists to Russia in 1766: Reports by Ivan Kulberg (Saratov: Saratov State Technical University, 2010): #6845.