29 April 1875
The Thirstland Trek is the name given to the exodus of Boer/Afrikaans families, most of them from the districts of Pretoria and Rustenburg, through Northern Bechuanaland to Angola, in search of a country where they could live according to their ideals and ideas.  The movement comprised of several separate treks from 1874 to 1905. It became known as the Thirstland Trek on account of the hardships the Afrikaners experienced in the desert. The first Thirstland Trek, which started in 1874 under the leadership of Gert Alberts, reached Lake Ngami on 29 April 1875. Feature: Afrikaner Treks
References

Wallis, F. (2000). Nuusdagboek: feite en fratse oor 1000 jaar, Kaapstad: Human & Rousseau;| Potgieter, D.J. et al. (eds)(1970). Standard Encyclopaedia of Southern Africa, Cape Town: NASOU, v. 10, p. 491