- Mar 5 Parma, Tuscany, Modena and Romagna vote in referendums to join the Kingdom of Sardinia
- Mar 7 22nd Grand National: Mr Tommy Pickernell aboard Anatis IRE wins
- Mar 9 1st Japanese ambassador arrives in San Francisco en route to Washington
- Mar 12 Congress accepts Pre-emption Bill: free land in West for colonists
- Mar 17 Japanese embassy arrives aboard Candinmarruh [sic]
- Mar 21 US extradition treaty with Sweden
- Mar 24 Clipper Andrew Jackson arrives in San Francisco, 89 days out of New York
- Mar 27 M L Byrn patents "covered gimlet screw with a 'T' handle" (corkscrew)
- Mar 28 First Taranaki War: The Battle of Waireka begins (New Zealand).
- Mar 29 Dion Boucicault's "Colleen Bawn" premieres in NYC