When Gallatin returned from Europe in September 1815, he declined Madison's request to take up his old post as Secretary of the Treasury. He did, however, help convince Congress to charter the Second Bank of the United States as a replacement for the defunct First Bank of the United States. Gallatin considered going into business with his longtime friend, John Jacob Astor, but ultimately he accepted appointment as ambassador to France. He served in that position from 1816 to 1823. Though he did not approve of the prevailing ideology of the Bourbon Restoration, Gallatin and his family enjoyed living in Paris. While serving as ambassador to France, he helped negotiate the Rush–Bagot Treaty and the Treaty of 1818, two treaties with Britain that settled several issues left over from the War of 1812 and established joint Anglo-American over Oregon Country.