St. Louis had a relationship with Mexico dating to trade along the Santa Fe Trail starting in the 1820s. It came to include commerce, marketing, and migration starting in the late nineteenth century, as Daniel Gonzales details here.
"A Gateway to the East: An Exploration of St. Louis’ Mexican History Through the Built Environment,"
The Confluence (2009-2020): Vol. 10
, Article 3.
Available at: https://digitalcommons.lindenwood.edu/confluence_2009/vol10/iss2/3