Family A44-14 in The Immigration of German Colonists to Denmark and Their Subsequent Emigration to Russia in the Years 1759-1766.
Family B-5 in The Immigration of German Colonists to Denmark and Their Subsequent Emigration to Russia in the Years 1759-1766.
Rus14-1 in The Immigration of German Colonists to Denmark and Their Subsequent Emigration to Russia in the Years 1759-1766.
Family #30 in the 1775 Grimm census.
Family #65 in the 1798 Grimm census.
Johann Wendel Adler was born in 1742 in Rhein-Neckar-Kreis, Baden-Wuerttemberg to Mr. Adler, first name unknown, and Catharina Zellerin. His mother's maiden name is almost certainly spelled incorrectly. There were no Zellerins that showed up in my search of birth and marriage records. It was probably Zeller or Zoeller.
Johann Wendel was an Evangelical Lutheran, a farmer in Rhein. During the mid 1700s, the southern tier of Germany had been hit hard with wars and famines, and many residents were poor farmers who could barely take care of their family's needs. 
In 1759, the Danish government offered these disadvantaged Germans a chance for a new life in Denmark, helping to farm what was currently unfarmable marshland. Those who chose to immigrate would be given an opportunity for a brighter future via homesteaded land or through a land lottery.
Johann Wendel arrived in Flensburg Denmark on 09 June 1762 with his wife Salome Hager, son Johann Michael, 12 weeks old and his mother-in-law Anna Margaretha Hager. He took his oath of allegiance to Denmark five weeks later on 19 July 1762, and was considered a reserve colonist.
The marshlands were very inhospitable to all farmers. Although Germans were known for being hardworking and good farmers with typical farm land, it was far more difficult to convert these former wetlands and grow crops. Most of the German immigrants barely reaped enough to feed their families, let alone to provide food for others in Denmark.
Around that same time, Catherine the Great invited Germans to immigrate to Russia. This offered Johann Wendel and his family a opportunity for a new, prosperous life. In 1765, he decided to immigrate with his family to Russia. It is unclear when the family left Denmark for Russia, but they are included on an immigration list of 57 German Danish colonists who traveled to Grimm, Russia.
At the time of the 1775 Grimm Census, he was living in Grimm with his wife and five children:
1775 Grimm Census 
By the time of the 1798 census, he was going by his middle name, Wendel, and his had a different wife, Christina Stend who was from the neighboring village of Moor (Klyuchi). Salome had been seven years older than her husband, and Christina was seven years younger. The sons still living with the family were from his first marriage: Johann Michael and Georg Jakob, along with their wives and children. Most likely his daughters were already married and living in another household.
1798 Grimm Census 
Wendel Adler is not listed in the 1834 census and was most likely deceased before 1816.  His death would have been documented in the 1816 male-only census. Had he survived to 1834, he would have been 92 years old. Had he survived to 1816, he would have been 74 years old, a significant long life for a Volga German during that time frame.
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