Noah engaged in trade and law, but when removing to Charleston, South Carolina, dedicated himself to politics.
In 1811, he was appointed by President James Madison as consul at Riga, then part of Imperial Russia, but declined, and, in 1813, was nominated Consul to the Kingdom of Tunis, where he rescued American citizens kept as slaves by Morroccan masters. Allegedly, Noah was removed from this position because, in the words of US Secretary of State James Monroe, his religion was "an obstacle to the exercise of [his] Consular function." The firing caused outrage among Jews and non-Jews alike.
Manuel Noah moved to New York, where he founded and edited The National Advertiser, The New York Enquirer (later merged into The Courier and Enquirer), The Evening Star, and The Sunday Times newspapers.
In 1819, Noah's most successful play, She Would Be a Soldier, was produced. That play has since established Noah as America's first important Jewish American writer. She Would Be a Soldier is now included in college level anthologies.
In 1820, in a precursor to modern Zionism, he tried to found a Jewish homeland at Grand Island in the Niagara River, to be called "Ararat," after Mount Ararat, the Biblical resting place of Noah's Ark. He erected a monument at the island which read "Ararat, a City of Refuge for the Jews, founded by Mordecai M. Noah in the Month of Tishri, 5586 (September, 1825) and in the Fiftieth Year of American Independence." Some have speculated whether Noah's utopian ideas may have influenced Joseph Smith, who founded the Latter Day Saint movement in Upstate New York a few years later. In his Discourse on the Restoration of the Jews Noah proclaimed his faith that the Jews would return and rebuild their ancient homeland. Noah called on America to take the lead in this endeavor.
The modern edition of Noah's writings is The Selected Writings of Mordecai Noah edited by Michael Schuldiner and Daniel Kleinfeld, and published by Greenwood Press.