He was also archivist and then librarian of the city of Frankfort.
After serving his native city as secretary and archivist, he became archivist to the national archives in Paris in 1866, and later librarian to the faculty of law.
His indefatigable work as archivist in the time when Napoleon was transferring so many treasures to Paris is not his least claim to the gratitude of scholars.
When in 1805 the principalities became part of Bavaria, Lang entered the Bavarian service (1806), was ennobled in 1808 and from 1810 to 1817 held the office of archivist in Munich.
Palacky had received a modest appointment as archivist to Count Sternberg and in 182 9 the Bohemian estates sought to confer on him the title of historiographer of Bohemia, with a small salary, but it was ten years before the consent of the Viennese authorities.
At the Restoration he was deprived of the post of archivist of the empire, which he had held from 1807, but from 1819 to 1830 (when he again became archivist of the kingdom) he held the chair of history and ethics at the College de France, and his courses were among the most famous of that age of public lectures.
In 1855 he was appointed archivist at Breslau; in 1862 he became professor of history at Heidelberg, and ten years later professor at Berlin, where he was a member of the directing body of the Monumenta and a member of the Academy.
He studied at Prague and at Olmiitz, and, after travelling extensively in search of historical material, became professor of history at the university of Prague and archivist for Bohemia in 1862.
In 1806 he was appointed secretary and archivist to the cabinet particulier of the emperor, whom he attended on his campaigns and journeys.