When did the creation of a single German state occur?

The creation of a single German state, often referred to as the Unification of Germany, occurred in 1871.

This event was the culmination of a series of wars and political maneuvering, culminating in the Franco-Prussian War of 1870-1871.

King Wilhelm I of Prussia was declared Emperor of Germany in the Hall of Mirrors at the Palace of Versailles on January 18, 1871.