The use of the unofficial nickname the Show-Me State has several possible origins.
The phrase “I’m from Missouri” means ‘I’m skeptical of the matter and not easily convinced’. This is related to the state’s unofficial motto of “Show Me,” whose origin is popularly ascribed to an 1899 speech by Congressman Willard Vandiver, who declared that “I come from a country that raises corn and cotton, cockleburs and Democrats, and frothy eloquence neither convinces nor satisfies me. I’m from Missouri, and you have got to show me.”
However, according to researchers, the phrase was in circulation earlier in the 1890s. According to another legend, the phrase was a reference to Missouri miners brought to Leadville, Colorado to take the place of striking miners and being unfamiliar with the mining methods there required frequent instruction, thus “Show-Me”.
It has also been known as the Puke State, perhaps on account of an 1827 gathering at the Galena Lead Mines.”…so many Missourians had assembled, that those already there declared the State of Missouri had taken a ‘puke.'”
Within the state, “pukes” referred before the Civil War to impoverished citizens who nonetheless supported slavery, the equivalent of “poor white trash.”Walt Whitman has listed “pukes” as a nickname for Missourians.
Missouri is also known as “The Cave State” with over 6000 recorded caves (second to Tennessee). Perry County has both the largest number of caves and the single longest cave in the state. Other nicknames include “The Lead State”, “The Bullion State”, “The Ozark State”, “Mother of the West”, “The Iron Mountain State”, and “Pennsylvania of the West”
There is no official state nickname; however. the official state motto is “Salus Populi Suprema Lex Esto”, Latin for “Let the welfare of the people be the supreme law.