Friedrich Heinrich (Fred) Jeppe emigrated to South Africa in January 1861, arriving in Durban in April. After some time he joined his eldest brother, Hermann O.C.F. Jeppe, in Potchestroom. A third brother, Julius, joined them in 1870. In December 1863 Fred married Susanna W. Truter. He appears to have been a merchant for some time, but in December 1866 was appointed as postmaster at Potchefstroom. In 1868 he became in addition Postmaster-General of the South African Republic. He introduced postage stamps of his own design in 1870, as well as mail carts linking the Transvaal to Natal, the Orange Free State and Cape Colony. In 1869 he was given the additional post of Treasurer-General of the republic. He was also a member of the government's Executive Council from 1871. In 1874 he was transferred to the seat of government, as postmaster of Pretoria. He gave up his post as Treasurer-General that year, and his remaining two posts the next year. Meanwhile the King of Portugal had named him a Knight of the Order of Jesus Christ in 1874, so that occasionally he used the title Chevalier. From 1878, during the British rule of the republic, he worked as a translator and interpreter of the Supreme Court and also compiled government statistics. At this time he served on the committee of the recently established Pretoria Public Library.
In 1868 Jeppe, with the help of Alexander A.B. Merensky*, compiled an Original map of the Transvaal or South African Republic on a scale of 1:1 850 000. It was the first topographic map of the territory compiled locally from farm diagrams and other information, including a compilation started in 1866 by Carl Mauch*. There was as yet no triangulation on which it could be based, and it contained no contours or spot heights. None the less it was surprisingly accurate and by far the best map of the territory up to that time. It was published as an annexure to Jeppe's first article, "Die Transvaal'sche oder Südafrikanische Republik, nebst einem Anhang: Dr. Wangemann's Reise in S.A.", in Petermann's Geographische Mitteilungen (1868, Vol. 24). Petermann added some information to the map that was not locally available. In the article Jeppe became probably the first person to ascribe a volcanic origin to the Pretoria Salt Pan (now regarded as an impact crater). His work led to his election as a fellow of the Geographical Society of London in 1874.
Some years later he published the Transvaal book almanac and directory for 1877, a compilation of useful information about the territory and its administration. Subsequent editions were published in 1879, 1881, 1887 and 1889. Also in 1877 he completed Jeppe's map of the Transvaal or South African Republic and surrounding territories... (scale 1:1 850 000), which was published in London. It included information provided by various explorers, whose routes are shown. He wrote a "Note on some of the physical and geological features to accompany (Jeppe's) new map of the Transvaal and surrounding territories", which appeared in the Quaterly Journal of the Geological Society of London (Vol. 47, pp. 217-250) that year. An index to the map, listing some 2000 features, was published in 1880. Through this work he became the most important cartographer of the Transvaal. He always acknowledged the sources of information received from others for inclusion in his maps.
In 1888 Jeppe described "The Kaap gold-fields of the Transvaal" in the Proceedings of the Royal Geographical Society and "Die Witwatersrand-Goldfelder in Transvaal" in Petermann's Mitteilungen. The next year he produced his third map, Map of the Transvaal or South African Republic and surrounding territories (scale 1:1 000 000, London, 1889). It was beautifully drawn and detailed, included the whole of the Orange Free State, Natal, Griqualand West and Lesotho, and was again the best map of the Transvaal to date. The name Johannesburg is shown on it for the first time and it included an index of all mining leases. This map was a remarkable achievement and was reprinted many times. It was followed by Jeppe's Schets kaart aantoonende de Zoutpansberg goudvelden (c. 1:531 000, Pretoria, 1893) and a paper on "The Zoutpansberg goldfields in the South African Republic" in the Geographical Journal. In 1896 he produced a Map of the southern goldfields of the Transvaal (1:253 440), with a geological section of the Banket formation by A.R. Sawyer*.
Meanwhile the government of the republic had requested him and Chief Justice J.G. Kotzé in 1882 to record all the laws of the country. This mammoth task resulted in De locale wetten der Zuid-Afrikaansche Republiek 1849-1885, bijeengebracht... door F. Jeppe en naauwkeurig herzien door J.G. Kotzé... (Pretoria, 1887-1889).
In 1891 Jeppe joined the civil service again, becoming chief computer in the office of the Surveyor-General. He visited Germany in 1897, but in July the next year fell ill from a liver ailment and died soon afterwards. At this time he was working on a cadastral map of the Transvaal in cooperation with his son, Carl F.W. Jeppe, based on surveys filed in the Surveyor-General's office. This Jeppe's map of the Transvaal or South African Republic and surrounding territories (scale 1:476 000) was printed on six sheets in Switzerland just before the outbreak of the Anglo-Boer War. Despite all precautions it became available to the British War Office, where it formed the basis of British military maps of the Transvaal. It was the first map of the Transvaal to show topographical detail and was the crowning achievement of nineteenth century South African cartography.
Jeppe was a modest man and versatile official, who kept out of politics. He was a Freemason, and served on the council of the Lutheran Church in Pretoria during the eighteen-nineties.