What was the first Buddhist text to be translated into English? When was it translated and by whom? Was it reasonably available to those interested and did it have much of an impact within academic circles and perhaps to the wider culture?
These seem to be the first Buddhist texts ever translated into English, published in 1693:
- THE LIFE OF THEVETAT, Translated from the Balie (i.e. Pāli)
- An Explication of the Patimouc, or Text of the Vinac
More information can be found in A philological approach to Buddhism by K. R. Norman, p. 4:
Simon de La Loubère [...] in 1687-88 went to Siam as an envoy of the king of France (King Louis), and on his return wrote a book about the Kingdom of Siam, which was published in France in 1691. Two years later an English translation was published in England. La Loubère gave a fascinating account of many aspects of Siam and Siamese culture, and he also included an account of the Siamese religion — Buddhism — and the sacred language of the Siamese. He noted the differences between that language, which he called Balie, and the Siamese language, and noted, correctly, the relationship between the former and Sanskrit. He also gave French translations of a few Buddhist texts.
Here is the English edition of Loubère's whole book, which contains the above-mentioned texts:
- A new historical relation of the kingdom of Siam by Monsieur De La Loubere ...; done out of French, by A.P. Gen. R.S.S. London: Printed by F.L for Tho. Horne ... Francis Saunders ... and Tho. Bennet ..., 1693.
Some other translations that can be regarded as quite early, include:
The History and Doctrine of Budhism: Popularly Illustrated: with Notices of the Kappooism, Or Demon Worship, and of the Bali, Or Planetary Incantations, of Ceylon by Edward Upham (London, 1829): contains translations of some Jātakas
None of these publications seem to have made a big impact.
In 1844 the magazine published Peabody's translation of a portion of the Lotus Sutra from French [...]. The publication ceased shortly thereafter in April 1844.
As to the first notable translation, I would give this honorary title to Max Muller's translation of Dhammappada, first published in 1869, later included in Muller's Sacred Books of the East series published around 1880s.
Beside Dhammapada, the series included important suttas such as Setting the Wheel of Dhamma in Motion, Mahaparinibbana, and others, all of Sutta-Nipata, most of Vinaya, one of the earliest post-canonical texts Milinda-panha, a Chinese version of the Life of Buddha by Asvaghosa, and some of the most important Mahayana texts such as Heart Sutra and Lotus Sutra.
Arguably this was the most notable early publication of Buddhist texts into English.
Sándor Csoma de Kőrös (Hungarian: Kőrösi Csoma Sándor) was a Hungarian-Szekler orientalist who went to Asia around 1820 looking for the ancestors of Hungarians, but ended up in Tibet instead. He is well known among Hungarians for his journey and for compiling the first Tibetan-English dictionary and grammar.
He spent considerable time in Tibet studying Tibetan and Buddhist philosophy between 1827-30. He was declared Boddhisatva in 1933 in Japan.
While I do not know if he translated Buddhist texts into English, it is plausible that he may have, as he immersed himself in Buddhism. Unfortunately it is unlikely that this will be easy to research on the internet, you may need to go to dusty old libraries to get definitive information ;-) Nevertheless, I thought that this was a good lead which is worth mentioning (since the dates are similar but a bit earlier than in the other answers).
Some of the earliest translations are covered in the Sacred Books of the East (Dhammapada by Max Müller based on a Latin translation by Viggo Fausböll and Sutta-Nipata by Viggo Fausböll) series by Max Müller in which some of the books are Buddhist books as per the Theravada tradition.