23 September 1838
On 23 September 1838 Gerhardus Marthinus (Gert) Maritz, Voortrekker leader, died at Sooilaer, in Natal (now kwaZulu Natal), he was 41 years old. The Great Trek in South Africa started in 1835 when over a three year period more then 12,000 Boers (farmers) left the Cape Colony. They trekked (moved) into the interior by ox wagon, in search of land where they would be free and beyond British control. Gert Maritz, along with Piet Retief was one of the leaders that advocated a migration as early as 1834, but the Great trek 'officially' began in 1835 when separate parties crossed the Orange River and headed towards the Transvaal.   
References

Wallis, F. (2000). Nuusdagboek: feite en fratse oor 1000 jaar, Kaapstad: Human & Rousseau|The Greenwood Histories of the Modern Nations. (2000) The History of South Africa. Greenwood Press: Westport, Conn and London