Mass Killings in the United States, Before 1900
Four or more killed, including suicides
One killer
By any criminal means
In one emotional event
==1805==
10 November 1805 Clarksburg WV, 9 killed (beaten) (http://murderpedia.org/male.C/c/clemmons-abel.htm)
==1806==
9 July 1806 Bowdoinham (?) ME 9 killed (ax) (https://touringmaineshistory.wordpress.com/2012/03/02/the-purrinton-tragedy-augusta-1806/)
==1840==
30 May 1840 Hill Valley PA, 6 Killed (multiple) (http://wc.rootsweb.ancestry.com/cgi-bin/igm.cgi?op=GET&db=rrrose2&id=I198697)
==1846==
11 September 1846 Overton County TN, 7 killed (?) (https://www.ancestry.com/boards/thread.aspx?mv=flat&m=879&p=surnames.o-27-neal)
==1860==
July & August 1860 US ship at sea, more than 29 slaves killed (mistreatment) (http://murderpedia.org/male.G/g/gordon-nathaniel.htm)
==1866==
7 April 1866 South Philadelphia PA, 7 killed (ax) (http://www.pennlive.com/life/2017/11/philadelphias_most_notorious_m.html)
==1871==
25 March 1871 Stonefort IL, 7 killed (?) (https://en.wikipedia.org/wiki/List_of_rampage_killers_(familicides_in_the_United_States))
==1878==
About 28 February 1878 Monroe County IL, 8 killed (arson) (https://en.wikipedia.org/wiki/List_of_rampage_killers_(familicides_in_the_United_States))
==1881==
17 July 1881 Eagle Creek WI, 9 killed (shot) (https://www.newspapers.com/newspage/79786752/)
==1882==
10 June 1882 Chicago IL, 5 killed (poisoned) (http://murderpedia.org/female.S/s/syeboldt-mary.htm)
==1885==
17 February 1885 Las Norias NM, 6 killed (assault) (https://en.wikipedia.org/wiki/List_of_rampage_killers_(familicides_in_the_United_States))
==1889==
1 March 1889 Okeechobee FL, 7* killed (shot) (https://en.wikipedia.org/wiki/Jim_Jumper_massacre)
==1894==
9 August 1894 Lincoln NE, 11 killed (sabotage of railroad) (https://en.wikipedia.org/wiki/1894_Rock_Island_railroad_wreck) unsolved
==1896==
26 May 1896 Campbell CA, 6 killed (multiple) (http://murderpedia.org/male.D/d/dunham-james.htm)
==1887==
6 August 1887 Bibb County GA, 9 killed (beaten) (http://murderpedia.org/male.W/w/woolfolk-thomas.htm)
25 December 1887 Worth County GA, 7 killed (multiple) (https://en.wikipedia.org/wiki/List_of_rampage_killers_(familicides_in_the_United_States))
==1893==
26 March 1893 Plain Dealing LA, 4 killed (shot) (https://en.wikipedia.org/wiki/List_of_school_shootings_in_the_United_States) No charges apparently, no word on number of killers.
==1896==
12 January 1896 Chicago IL, 7 killed (poison) (https://en.wikipedia.org/wiki/List_of_rampage_killers_(familicides_in_the_United_States))
5 February 1896 Chicago IL, 7 killed (shot) (https://en.wikipedia.org/wiki/List_of_rampage_killers_(familicides_in_the_United_States))
13 January 1896 Marysville KS, 8 killed (poison) (https://en.wikipedia.org/wiki/List_of_rampage_killers_(familicides_in_the_United_States))
25 May 1896 Campbell CA, 6 killed (multiple) (https://en.wikipedia.org/wiki/List_of_rampage_killers_(familicides_in_the_United_States))
==1897==
26 September 1897 Carrolton IA, 8 killed (shot) (https://en.wikipedia.org/wiki/List_of_rampage_killers_(familicides_in_the_United_States))
==1898==
18 July 1898 Oakland CA, 7 killed (explosion) (https://en.wikipedia.org/wiki/List_of_rampage_killers_(Americas))
there doesn't seem to be anything here