Rosetta Stone - Wikipedia

On July 19, 1799, the Rosetta Stone, a tablet with hieroglyphic translations into Greek, is found in Egypt. From the article:

"The Rosetta Stone is a granodiorite stele, found in 1799, inscribed with three versions of a decree issued at Memphis, Egypt in 196 BC during the Ptolemaic dynasty on behalf of King Ptolemy V. The top and middle texts are in Ancient Egyptian using hieroglyphic script and Demotic script, respectively, while the bottom is in Ancient Greek. As the decree has only minor differences between the three versions, the Rosetta Stone proved to be the key to deciphering Egyptian hieroglyphs.

The stone, carved in black granodiorite during the Hellenistic period, is believed to have originally been displayed within a temple, possibly at nearby Sais. It was probably moved during the early Christian or medieval period, and was eventually used as building material in the construction of Fort Julien near the town of Rashid (Rosetta) in the Nile Delta. It was rediscovered there in July 1799 by a French soldier named Pierre-François Bouchard during the Napoleonic campaign in Egypt. It was the first Ancient Egyptian bilingual text recovered in modern times, and it aroused widespread public interest with its potential to decipher this previously untranslated hieroglyphic language. Lithographic copies and plaster casts began circulating among European museums and scholars. Meanwhile, British troops defeated the French in Egypt in 1801, and the original stone came into British possession under the Capitulation of Alexandria and was transported to London. It has been on public display at the British Museum almost continuously since 1802, and is the most-visited object there.

Study of the decree was already under way when the first full translation of the Greek text appeared in 1803. It was 20 years, however, before the transliteration of the Egyptian scripts was announced by Jean-François Champollion in Paris in 1822; it took longer still before scholars were able to read Ancient Egyptian inscriptions and literature confidently. Major advances in the decoding were recognition that the stone offered three versions of the same text (1799); that the demotic text used phonetic characters to spell foreign names (1802); that the hieroglyphic text did so as well, and had pervasive similarities to the demotic (Thomas Young, 1814); and that, in addition to being used for foreign names, phonetic characters were also used to spell native Egyptian words (Champollion, 1822–1824).

Ever since its rediscovery, the stone has been the focus of nationalist rivalries, including its transfer from French to British possession during the Napoleonic Wars, a long-running dispute over the relative value of Young and Champollion's contributions to the decipherment and, since 2003, demands for the stone's return to Egypt.

Two other fragmentary copies of the same decree were discovered later, and several similar Egyptian bilingual or trilingual inscriptions are now known, including two slightly earlier Ptolemaic decrees (the Decree of Canopus in 238 BC, and the Memphis decree of Ptolemy IV, c. 218 BC). The Rosetta Stone is, therefore, no longer unique, but it was the essential key to modern understanding of Ancient Egyptian literature and civilisation. The term Rosetta Stone is now used in other contexts as the name for the essential clue to a new field of knowledge."