King Frederick William IV of Prussia reigned from 1840 to 1861. He was known for his romantic ideals and his vision of a united Germany. Frederick William IV was a member of the Hohenzollern dynasty and was often referred to as the "Romanticist King" due to his interest in art and culture. During his reign, he faced significant political challenges, including the Revolutions of 1848 that swept across Europe. Although he initially promised reforms, he later rejected the idea of a constitutional monarchy, which led to discontent among his subjects. His reign ultimately ended without achieving the unification of Germany.