Noted by Henry Lichtenstein in 1803 in his travels through the Hantam and the Roggeveld. There was a farmhouse in the poort lived in by someone called Bruyere; there was a fruit orchard and cornfields, and a small wood of oaks and poplars by a stream.

W.J.Burchell described it in 1811 when he outspanned his two oxwagons under two large Karee trees as "the door to the desert".

1827 there were several routes from Cape Town to the hinterland and in 1848 there was only one very difficult road from Tulbagh to Ceres which crossed the Witzenberg by Mostert's Pass.

1848 the new road through Mitchells Pass was opened (Andrew Geddes Bain); the road then continued through Karoopoort to Sutherland.

1852 the road through Bain's Kloof was opened.

1850 marked the opening of an inn at Karoopoort.

1870 the diamond fields of Kimberley were discovered and a weekly service between Cape Town and Kimberley was started by the Diamond Fields Transport Company. Speculators, diggers, and fortune-seekers passed through Karoopoort in their hundreds. At times there were as many as 30 ox, mule, and horse-wagons travelling through the pass behind one another. Goods transported were hardware, tobacco, wine, brandy, biltong, dried and fresh fruit, vegetables, skins, and mine machinery.

After Ceres the first outspan was at Kafferskraal, the next at Leeufontein, (where the owner had put aside a stretch of ground for that purpose); travellers could overnight at the old Leeufontein homestead; the third outspan was at Hottentotskloof, and the fourth at Karoopoort. The following two outspans were at Platfontein and Smitswinkel.

Soon after this a coach service was started by the Inland Transport Company; they used strong, light wagons which would carry fourteen people including the driver and his two assistants. The sides of the wagon were open but could be closed by lowering canvas shutters to keep out the heat or the rain; each wagon was drawn by 10 Cape mules which had bells around their necks. The service ran from the end of the railway line at Wellington, through Bain's Kloof and Mitchell's Pass to Ceres, and then via Karoopoort to Beaufort West and Kimberley.

1850 - 1900: an inn was established at Karoopoort (the separate barn at the south side of the building); the land was leased from the state with the proviso that travellers could overnight there free.

The Forgotten Highway began to decline in 1875 when the railway line from Wellington reached Tulbagh Rd; by the end of 1876 it had reached Wolseley, and by 1877 it had gone as far as Touws River.

1877 also marked the opening of the Pakhuis Pass from Clanwilliam to Calvinia; whereas previously the only route had been through Karoopoort, it was now quicker to go via Clanwilliam and there was better accommodation available along the route.

1895 marked the end of the busy years for Karoopoort and the road became less and less frequented.

Many famous people passed that way on their way to Kimberley (Rhodes, Dr Livingstone, Le Vaillant etc)

1981 Karoopoort declared a National Monument and 1994 restored by the state.