- Jun 1 US adventurer William Walker conquers Nicaragua, reestablishes slavery
- Jun 2 The Portland Rum Riot occurs in Portland, Maine
- Jun 5 Anti-foreign anti-Roman Catholic Know-Nothing Party's 1st convention
- Jun 13 Opera "Les Vêpres Sicilenne" is produced (Paris)
- Jun 17 Heavy French/British bombing of Sebastopol, Crimea: 2,000+ killed
- Jun 20 Commissioners appointed to lay out San Francisco streets west of Larkin
- Jun 28 The Sigma Chi Fraternity was founded at Miami University