| SURNAME | TOWNSHIP | RESEARCHER |
| Yarmouth/Yarmuth | Verdell Leikam | |
| Yopp | Antioch | Donna McIlravy |
| Yore | Deerfield, Everett, Lake Forest; about 1846 | Cindy Dorfler-Hederer or Sharon Dorfler Kemble |
| Young | Wadsworth, 1878 | Pamela Young or Pamela Young |
| Younghen | Pete Velsko | |
| Younglove | Avon | Grace Younglove Hudson |
| Zdan | North Chicago, 1909-1991 | Ruth Suchanski Kelly |
| Zdanowicz | North Chicago, 1907-1958 | Ruth Suchanski Kelly |
| Zuhde | Antioch | Dawn (Hanke) Knauft |