Holy-Moly ! ! !
Missourri is, indeed, one of the most free States in the Union with regard to carrying guns:
"Missouri allows open carry without a permit, so long as the firearm is not displayed in an angry or threatening manner. Some localities prohibit open carry; however, concealed carry license holders are exempted from this restriction.
Missouri does not prohibit the open carry of any specific weapon, nor do most of the restrictions in RSMo 571.030 apply to the open carry of a firearm or other weapon. It is not a crime under Missouri law to openly carry a weapon into any place where concealed carry is prohibited, except for a church, school bus, school, or onto the grounds of a school function. According to RSMo Section 571.030, there is no age limit to openly carry a handgun, long gun or any deadly weapon.
Ref: Wikipedia
:::EDITED TO ADD :::
The interested reader, if any, can find a comprehensive ranking of firearm-friendly States at Guns and Ammo.
Missouri ranks #12
#1 is Arizona
#51 is New York