One of Cluss's school friends: Wilhelm Pfaender (1826 - 1905), like Cluss an enthusiastic gymnast in his youth who emigrated to the USA in 1847.
Among Adolf Cluss's friends in Heilbronn were the brothers Wilhelm and Carl Pfaender. Wilhelm Pfaender (1826 ? 1905) was his schoolmate; like Cluss, he was an enthusiastic member of a sports club ("Turnverein") and was also to emigrate to the United States. Wilhelm Pfaender paticipated in the founding of the town New Ulm, Minnesota. Carl Pfaender (1819 - 1876) belonged, like Adolf Cluss, to the inner circle around Karl Marx and lived in London from 1845 on.
In his youth, Cluss was also "close friends" with August Bruckmann (1824 - 1864). Son of a silverware manufacturer, Bruckmann was a member of the Heilbronn "Turnverein", which he headed in 1848 and 1849. He played an active part in the revolution of 1848; after a brief imprisonment, he emigrated to France and later relocated to Russia.
We know for certain that Adolf Cluss knew Wilhelm Doderer (1825 - 1900), a classmate of the same age who also attended the "Realklasse" of Heilbronn "Gymnasium". After 1840, Doderer worked "with an industrious construction foreman" a a mason and stonecutter on Kilian's Church before he passed the Wuerttemberg state exam in the building trades and attended the Berlin Academy of Architecture. This career path was typical of architects in the 19th century.
Carl Cluss (1819 - 1870), Adolf's older brother, also became an architect. After finishing school, he became an apprentice mason and stonecutter in his father's firm. He passed his master's exam in 1844, and then, like Doderer, went on to study architecture in Berlin.