Short answers, pulled from the story.
Delegates in Missouri cast a vote of 98 to 1 against leaving the Union on the 19th of March 1861. This decision kept Missouri within the United States despite pressure from Governor Claiborne Fox Jackson.
Sterling Price led the convention as its president and shared a moderate stance with most of the state's population. He neither favored secession nor supported waging war against the South at that moment.
Captain Nathaniel Lyon arrested the encampment after discovering artillery hidden within the camp. The march of prisoners through town sparked a violent riot that shifted political power toward secessionist factions.
Governor Jackson signed the bill guaranteeing separation from the Union on the 31st of October 1861. The legislature had passed the bill two days earlier on the 30th of October after debating it since the 28th of October.
The Confederate Congress admitted Missouri as its 12th state on the 28th of November 1861 following the Neosho ordinance. This admission occurred after Jackson's government named Senators to serve in the Confederate Congress before being driven into exile.