In the early 19th century, democratic movements in Denmark began to gain momentum, but King Frederick VI offered only limited concessions, such as establishing Consultative Estate Assemblies (Rådgivende Stænderforsamlinger) in 1834. These assemblies provided a platform for political movements, including the National Liberals and the Friends of Peasants, who became key players in the push for democratic reforms. When Christian VIII ascended to the throne in 1839, he continued the policy of making minor concessions while maintaining the absolute monarchy.
At this time, Denmark was part of the Unitary State (Helstaten), a personal union that included the Duchies of Schleswig, Holstein, and Lauenburg. The "Schleswig-Holstein question" was a significant source of tension. The National Liberals, under the slogan "Denmark to the Eider," advocated for Schleswig to become an integral part of Denmark, while separating Holstein and Lauenburg. Holstein and Lauenburg were members of the German Confederation, but Schleswig was not, creating a complex political dynamic. Meanwhile, German nationalists in Schleswig sought to keep Schleswig and Holstein united and to have Schleswig join the German Confederation.
Christian VIII recognized that a constitution encompassing both Denmark and the Duchies was necessary for maintaining the Unitary State and advised his son and successor, Frederick VII, to pursue such a constitution. After Christian VIII's death in January 1848, European revolutions intensified demands for change in Denmark. By March 1848, the Schleswig-Holstein question had reached a boiling point, with an ultimatum from Schleswig and Holstein demanding reforms. Simultaneously, political pressure from the National Liberals increased. In response, Frederick VII dismissed his government and appointed the March Cabinet, which included four leaders from the Friends of Peasants and the National Liberals, such as Ditlev Gothard Monrad and Orla Lehmann. Rejecting the ultimatum from the Duchies, Denmark entered the First Schleswig War.
During the conflict, work began on drafting a new constitution for Denmark. D.G. Monrad took the lead in drafting, and Orla Lehmann edited the document. Influenced by the Constitutions of Norway (1814) and Belgium, the draft was presented to the Constitutional Assembly of the Realm (Den Grundlovgivende Rigsforsamling), a body consisting of 114 elected members and 38 appointed by the king. The assembly was divided among the National Liberals, the Friends of Peasants, and the Conservatives. Central debates focused on the structure of the political system and election rules.
On May 25, 1849, the Constitutional Assembly approved the new constitution, and it was signed by Frederick VII on June 5, 1849, a date now celebrated as Constitution Day in Denmark. Known as the June Constitution, this document established the Rigsdag, a bicameral parliament comprising the Landsting (upper house) and the Folketing (lower house). Although voting rights for both chambers were identical, elections to the Landsting were indirect, and the eligibility requirements were more stringent. Overall, the constitution granted voting rights to approximately 15% of the population. Due to the ongoing First Schleswig War, the constitution was not immediately applied to Schleswig, with this issue postponed until after the war's conclusion.