Final answer:
Frederick William IV, the 2nd Hohenzollern absolute monarch, ruled Prussia from 1840 until 1861 - a 21-year reign and was often called the Romantic Monarch for his cultural and architectural interests and idealistic viewpoint of politics.
Step-by-step explanation:
The 2nd Hohenzollern absolute monarch was Frederick William IV of Prussia. He ruled from 1840 until 1861, therefore a 21-year reign. Frederick William IV is often referred to by his nickname, the Romantic Monarch due to his cultural and architectural interests as well as his romantic views on politics.
Notably, he declined the title Emperor of Germans offered by the Frankfurt Assembly, arguing that he could not accept a crown by the 'people's grace' because his role as monarch was divine. Eventually, after his reign, the unification of Germany was signalled by the increasing influence of the Zollverein.
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