- Apr 1 New Constitution adopted by the German Empire
- Apr 10 William Hammond Hall's maps & surveys of Golden Gate Park accepted
- Apr 14 Canada sets denominations of currency as dollars, cents, & mills
- Apr 20 US 3rd Enforcement Act (President can suspend writ of habeas corpus)
- Apr 22 All German Jews emancipated after the German Constitution adopted by its last state Bavaria
- Apr 23 Blossom Rock in San Francisco Bay blown up
- Apr 30 The Camp Grant Massacre of Apaches in Arizona Territory, perpetrated by white & Mexican adventurers; 144 die