Village in the Willem Pretorius Game Reserve near the Sand River, 30 km from Winburg. The name is derived from the Allemanskraal dam, some 9 km to the North-West. The Sand River Convention was signed there in 1852, which gave independence to the South African Republic.
References
New Dictionary of South African Place Names by Peter E. Raper.
https://www.linx.co.za/tripreports/allemanskraaldam/index.php
Further Reading
https://www.encyclopedia.com/history/encyclopedias-almanacs-transcripts-and-maps/sand-river-convention
https://www.britannica.com/topic/Sand-River-and-Bloemfontein-conventions
https://www.safarinow.com/destinations/winburg/hub.aspx