Borckenhagen was born on 21 February 1852 in Minden-Rodenbeck, Germany, the son of a Prussian officer in the Franco-Prussian War. He emigrated to southern African in 1873 due to poor health, settling in the Orange Free State. He began work as an ambitious journalist, and swiftly rose to a position of extreme influence in the republic. After working for a while on a publication, De Boerenvriend Huisalmanak, he became the founder and editor of its successor, the Free State Express newspaper, in 1877. He also acquired the printing press of Frederick Schermbrucker (an incendiary and deeply unpopular politician) and built the business into the biggest media source in the republic. As an aside to his increasing political work, he continued to run that powerful publication for the remainder of his life.
Borckenhagen propounded strong anti-imperialist views, and as a republican, fought for a united and independent South Africa. He strongly influenced the politicians Francis William Reitz and Martinus Theunis Steyn, serving as a mentor for the two men who later became Presidents of the Orange Free State. Borckenhagen came to have a massive influence over many other leaders across southern Africa, and excelled at discreetly influencing politicians with persuasive argument.
Under his direction, Reitz and other leaders joined him in founding the Afrikaner Bond in 1881, as a political organisation for all those who, regardless of ancestry, considered Africa to be their home rather than Europe. In April 7, 1881, he wrote the constitution of the new Bond, and published its manifesto in the Express, declaring it to be for "..the States of South Africa to be federated in one independent republic.", free from British Imperialism. As a first step to this goal, he favoured a union between the two Afrikaner republics, as a bulwark against British imperialism. To this effect he took the position of Secretary of the Commission from Orange Free State Volksraad, to the Transvaal Republic, on May, 1887. 
With the rise to power of Cecil Rhodes, Borckenhagen quickly became aware of the pivotal importance of this arch-imperialist in the future of southern Africa. Making an estimation of the level of Rhodes's personal ambition and keen to neutralise an impending wave of imperialism, Borckenhagen met Rhodes and attempted to divert him to the republican cause, using the temptation of power. Having successfully influenced Rhodes to desire a united South Africa by offering him its leadership, he finally failed to persuade Rhodes to support complete independence for South Africa. He famously confronted Rhodes in Cape Town, in an oft-quoted interview, of which several conflicting versions exist. Borckenhagen reportedly accused Rhodes of "crass materialism", a reverence for money, and the intention of forcefully bringing the republics into the British Empire. Rhodes reported that, in response to Borckenhagen's insistence that any union of South Africa would need to be independent, he had replied: "No, you take me either for a rogue or a fool. I would be a rogue to forget all my history and traditions; and I would be a fool, because I would be hated by my own countrymen and mistrusted by yours." Failing to influence Rhodes, as he had so many politicians in the past, Borckenhagen moved to stand squarely in opposition to him. He gained considerable following in the ensuing years as he was perceived as the only Free Stater capable of combating Rhodes's plans. As stated in "Lord Milner and South Africa", The Express (Mr. Borckenbagen's paper) has of late been the only paper in South Africa that has been able to hold its own against the Rhodesian flood. This was owing to Mr. Borckenhagen's intelligence and independence.  
Borckenhagen remained a leader of the Bond until his death in 1898 in Bloemfontein. His strategies and ideas continued to exercise a huge influence on republican politicians throughout southern Africa, such as du Toit of the Genootskap van Regte Afrikaners in the Cape Colony. However it was in the Orange Free State that his influence was strongest; as related by Basil Worsfold: "(Borckenhagen) was probably the most consistent of all the South African exponents of the nationalist creed. Certainly it is no exaggeration to say that he converted the Free State of Brand into the Free State of Steyn."
After his death, he was laid to rest in President Brand Cemetery, Bloemfontein, and his paper was taken over by his widow, Mary Dorothea Blackmore, before it was captured and closed by the British during the Anglo-Boer War. He was also survived by his seven children. 
- A. Strauss: Die rol van Carl Borckenhagen, redakteur van De Express, in die Oranje-Vrystaat, 1877-1888. Universiteit van die Oranje-Vrystaat, 1985.
- J. L. McCracken: The Cape Parliament. Clarendon Press: Oxford. 1967.