- Mar 1 1st federal land bank chartered in USA
- Mar 1 US government releases the plain text of the "Zimmermann Telegram" to the public; Germany proposed reward to Mexico if they joined war against the US
- Mar 2 Jones Act: Puerto Rico territory created, US citizenship granted
- Mar 3 First major strike of the Russian "February Revolution" starts at the giant Putilov factory in Petrograd [OS=Feb 18]
- Mar 3 German Foreign Secretary Arthur Zimmermann publicly admits the "Zimmermann Telegram" is genuine; revelation generates support for the US declaration of war on Germany in April.
- Mar 3 Mexico and the USA renew diplomatic relations
- Mar 3 US Congress passes 1st excess profits tax on corporations
Woodrow Wilson 2nd Term
Mar 5 US President Woodrow Wilson is inaugurated for a second term
- Mar 7 1st jazz record released on a 78 by Original Dixieland Jass Band for the Victor Talking Machine Company ("Dixie Jazz Band One Step," one side "Livery Stable Blues" other)
- Mar 8 Russian "February Revolution" begins in earnest with protests celebrating International Woman's Day and riots in St Petersburg over food rations and conduct of the war [OS=Feb 23]
- Mar 8 US Senate introduces the Cloture Rule, requiring a two-thirds majority to end debate, at the urging of Woodrow Wilson [1]
- Mar 10 Batangas was formally founded as one of the Philippines's earliest encomiendas
- Mar 11 1st NHL championship game ever played, Toronto Arenas beats Montreal Canadiens 7-3 in 1st of 2 game set (second game on March 13)
- Mar 11 British forces occupy Baghdad, the capital of Mesopotamia, after Turkish forces evacuated
- Mar 12 A German submarine sinks an unarmed US merchant ship, the 'Algonquin' on the same day that US President Woodrow Wilson gives executive order to arm US merchant ships
- Mar 12 In the wake of the February Revolution, Communist Party members Joseph Stalin, Lev Kamenev and Matvei Muranov arrive in Petrograd (St Petersburg) and seize control of the Pravda newspaper
- Mar 12 [OS Feb 27] Russian Duma sets up the Provisional Committee; Soviets form Executive Committee
Nicholas II Abdicates
Mar 15 The last Russian Tsar Nicholas II, abdicates and nominates his brother Grand Duke Michael to succeed him [OS Mar 2]
- Mar 16 Russian Grand Duke Michael, brother of Tsar Nicholas II defers acceptance of the Russian throne [OS Mar 3]
- Mar 17 1st exclusively women's bowling tournament begins in St Louis, Missouri
- Mar 17 Delta Phi Epsilon is founded at New York University Law School
- Mar 19 US Supreme Court uphoelds 8-hr work day for railroad employees
- Mar 19 Victor Herbert and Harry Blossom's operetta "Eileen", loosely based on a novel by Herbert's grandfather, premieres at Shubert Theater, New York City
- Mar 20 After the sinking of 3 more American merchant ships, US President Woodrow Wilson meets with cabinet, who agree that war is inevitable
- Mar 21 Loretta Walsh becomes US Navy's 1st female Petty Officer
- Mar 22 The USA is the first nation to recognize the new government of Russia
- Mar 23 Tornadoes kills 211 over 4 days in Midwest US
Bill Bishop's 1st Victory
Mar 25 Canadian flying ace Billy Bishop claims his first victory, shooting down and mortally wounding German Leutnant Theiller
- Mar 26 British win a battle against Turks at Gaza
- Mar 26 Stanley Cup Final, Seattle Ice Arena, Seattle, WA: Seattle Metropolitans (PCHA) beat Montreal Canadiens (NHL), 9-1 for a 3-1 series victory; first US team to win SC
- Mar 28 Jews are expelled from Tel Aviv & Jaffa by Turkish authorities
- Mar 28 Puccini's "La Rondine" premieres in Monte Carlo
- Mar 31 The Danish West Indies are officially ceded to the US for $25 million and renamed the Virgin Islands
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