King Wilhelm I of Prussia was born on March 22, 1797, and became the King of Prussia in 1861. He played a crucial role in the unification of Germany, which was achieved in 1871. Wilhelm I was known for his strong leadership and support of military reforms, which helped strengthen the Prussian army. Under his reign, the German Empire was proclaimed in the Hall of Mirrors at the Palace of Versailles, marking a significant moment in European history. Wilhelm I appointed Otto von Bismarck as his Chancellor, who was instrumental in the unification process. Wilhelm I ruled until his death on March 9, 1888.