Editing 1803 (section)

=== January–March ===
* [[January 1]] – The first edition of [[Alexandre Balthazar Laurent Grimod de La Reynière]]'s ''Almanach des gourmands'', the first guide to restaurant cooking, is published in Paris.
* [[January 4]] – [[William Symington]] demonstrates his ''[[Charlotte Dundas]]'', the "first practical steamboat", in Scotland.
* [[January 30]] – [[James Monroe|Monroe]] and Livingston sail for Paris to discuss, and possibly buy, [[New Orleans]]; they end up completing the [[Louisiana Purchase]].<ref>{{cite web |url=http://www.historyorb.com/events/date/1803 |title=Historical Events for Year 1803 &#124; OnThisDay.com |website=Historyorb.com |access-date=August 4, 2016 |archive-url=https://web.archive.org/web/20150630071746/http://www.historyorb.com/events/date/1803 |archive-date=June 30, 2015 |url-status=live }}</ref>
* [[February 19]]
** An [[Act of Mediation]], issued by [[Napoleon Bonaparte]], establishes the [[Swiss Confederation (Napoleonic)|Swiss Confederation]] to replace the [[Helvetic Republic]]. Under the terms of the act, [[Graubünden]], [[Canton of St. Gallen|St. Gallen]], [[Thurgau]], the [[Ticino]] and [[Vaud]] become Swiss cantons.
** [[Ohio]] is admitted as the 17th U.S. state.<ref>{{cite web |title=Ohio Statehood &#124; OhioHistoryCentral.org |url=http://ohiohistorycentral.org/w/Ohio_Statehood |access-date=October 7, 2019 |archive-date=October 7, 2019 |archive-url=https://web.archive.org/web/20191007165856/http://ohiohistorycentral.org/w/Ohio_Statehood |url-status=live }}</ref>
* [[February 20]] – [[Kandyan Wars]]: [[Kandy]], Ceylon is taken by a British detachment.
* [[February 21]] – [[Edward Despard]] and six others are hanged and beheaded for plotting to assassinate King [[George III of the United Kingdom]], and to destroy the [[Bank of England]].
* [[February 24]] – ''[[Marbury v. Madison]]'': The [[Supreme Court of the United States]] establishes the principle of [[judicial review]].
* [[February 25]] – A major redistribution of territorial sovereignty within the [[Holy Roman Empire]] is enacted, via an act known as the ''[[Reichsdeputationshauptschluss]]''.
* [[March 9]] – [[Aargau]] becomes a Swiss canton.