This Day in Jewish History First Minyan Forms in Chicago, Promptly Splits

They also formed what wasn't actually the first synagogue in the midwest, Kehilath Anshe Maarav.

October 11, 1845, is the day noted by history as the first time a minyan (Jewish prayer quorum of 10) convened in Chicago. Within two years, the group that met that Yom Kippur day had organized themselves into the city’s first synagogue, and three years after that, the congregation had - as befits any self-respecting Jewish organization - split into two.