Mass murdered gravesite in US?

Question

Not counting war crime type things, terrorist attacks, accidents, etc.

What is the largest find of murdered victims in the US? For example, like in Season 2 of Dexter, 18 bodies are found.

Answer 1

in Chicago. confederate prisoners slaughtered by  federal troops and Indians during Civil war. this was murder.

Answer 2

Desert in Nevada Mob executions near Las Vegas.

Answer 3

Belle Gunness , LaPorte, Indiana" Gunness probably killed at least 25 people and possibly as many as 33"

I'm sure somebody out there is going to say the Branch Davidian cult......