Leopold I, King of the Belgians. He was born as Prince of Saxe-Coburg-Saalfeld and he was the founder of the Belgian line of the House of Saxe-Coburg-Gotha. His children included Leopold II of Belgium and Empress Carlota of Mexico. He was born in Coburg and died in Laeken. He swore allegiance to the constitution in front of the Saint Jacob's Church at Coudenbergh Place in Brussels on 21 July 1831. This day became the Belgian national holiday.