Here in Wood Dale, IL in the near NW suburb of Chicago:
Daytime: nothing but 640 splatter
Nighttime: solid WSM
DX/RETRO: only 3 other stations besides WSM heard on 650 kHz: WKKQ (now WNMT, Nashwauk, MN), CKOM (Saskatoon, SK), and HRVW, La Voz de Centro America, San Pedro Sula, Honduras. As far as I can remember, I have never noticed WSM off the air opening any opportunities for DX on the frequency.
Only 5 kHz above on the split frequency of 655 kHz Radio Nacional, San Salvador, El Salvador used to be a common log in the Chicago area back in the 1980's.