that the largest mass-execution (or just plain execution, I assume) in United States history took place. 38 men were hanged in downtown Mankato, Minnesota of all places. It was a mass hanging, so all 38 men were placed on a giant scaffold and hung at the same time. Some reports say that the men held hands before the gallows dropped.
Incredibly, the number of men that the State of Minnesota wanted to hang was nearly 800% higher. Specifically, the state wanted to execute 303 men. President Lincoln, however, commuted the death sentences of 264 of men the state wanted to execute. You can listen to a This American Life broadcast about the execution and events that precipitated it here. Or if hearing about mass death is not your cup of tea, you can listen to Jimmy Durante sing Frosty the Snowman here.
Of course, one can't commute the death sentence of 264 people without some paperwork problems. Hence, a man named Chaska was hung despite the fact that President Lincoln had included him on the list of men to be spared.
In any event, it is safe to say that Minnesotans celebrate the holidays differently in 2012 than they did in 1862.