While he studied law, Irving amused himself by writing for periodicals such essays on New York society and the theater as the Letters of Jonathan Oldstyle, Gent. (1802–3). From 1804 to 1806 his older brothers financed his tour of France and Italy. On his return he joined William Irving and J. K. Paulding in publishing Salmagundi; or, The Whim-Whams and Opinions of Launcelot Langstaff & Others (1807–8), a series of humorous and satirical essays. Under the pseudonym Diedrich Knickerbocker, he published A History of New York (1809), a satire that has been called the first great book of comic literature written by an American. Purporting to be a scholarly account of the Dutch occupation of the New World, the book is a burlesque of history books as well as a satire of politics in his own time.