I am also researching my Ahlmann ancestors from Pomerania (82 so far) and will list a few here, hoping some of my data will connect with yours (or someone else reading this). -- Please let me know.
Some of our oldest data (from Trinity Lutheran Kirchenbuch, North Morristown, MN) is of Johann Ahlmann I (b. est. 1790's?) who married Bertha Berndt, and lived in 'Pommern' (now Poland). They had at least three sons, one of whom was Joachim Ludwig Ahlmann, b. Nov. 30 1825 in Germany. He often went by the name of ' J. Ludwig', and he married Caroline Bundt who died (of tuberculosis?) in Germany between 1883 and 1888.
As a widower he emmigrated aboard the "Main", arriving in the U.S. Aug. 22, 1888. His occupation was listed as "Maurer" (census agrees, as does family tradition: he was a stonemason). He died Mar. 13, 1902 at Morristown, MN of old age at 76 yr, 3 mo 13 days.
Two of his sons and their wives and three infant grand children had previously emmigrated in 1883 and 1886. The two sons were: Johann Christian Ahlmann II (we have data on his wife and 10 Ahlmann children) and Hermann Ernst Ludwig Ahlmann b. Oct. 29, 1849, d. Apr. 8, 1898 at N Morristown, MN.
Hermann's wife was Bertha Louise Schmidtke b. July 11, 1851, d. Apr. 7, 1915 and they had eight children, three of whom survived: Bertha Ahlman Cross (1891-1956), Gustav Ahlman (1888-1979) and Franz "F. H." Ahlman (1880-1949).
Grandpa Franz Ahlman and Grandma Martha had nine children, seven of whom survived, including my own father, M. J. "Cap" Ahlman (1913-1965). Others include Wilhelm August Ahlmann (1909-1931, died in a car accident) and Arthur Gustav Robert Ahlman (1905-1979).
This Grandpa Franz Ahlman(n) was born in Besswitz, Kr. Rummelsburg, Pommern and his wife, Grandma Martha Smuda-Von Trebiatowski Ahlman (1886-1940) was born in Briesen, Kr. Schlochau, West Prussia (both now in Poland).
Grandma Martha's father, Josef Smuda-Von Trebiatowski married my Great Grandma Caroline Lange, whom I remember fondly. She had been born Dec. 18, 1864 in West Prussia, d. Feb. 11, 1945, buried at Calvary Catholic Cemetary, Faribault, MN.