According to "Birds of Missouri", Latest date:  10, Sept 1961.  He does add, though:
"Widmann (1907) states, without giving any details, that birds are recorded until the end of Sept."
A book I have from 1947 by Sterling P. Jones, "Migratory and Permanent Resident Birds" in the St. Louis Region, gives the date of 9/30 fro departure.
Looks like you have a late bird!
Pat Lueders, Webster Groves, MO

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