"Many" is overstating it a little. There's probably six or seven, but when you consider metro area populations the number of sub-100K AHL areas is probably two or three.
Forgiveness please, but used most honorable google-fu to compile populations of AHL cities.
Springfield MA 153,552
Manchester NH 110,209
Binghamton NY 46,551
Wilkes-Barre/Scranton PA 41,243+75,809
Albany NY 97,904
Norfolk VA 245,782
Providence RI 178,432
St. John's NL 100,645
Hershey PA 14,257
Worcester MA 182,669
Glens Falls NY 14,609
Syracuse NY 144,170
Portand ME 66,214
Bridgeport CT 146,425
Hartford CT 124,893
Grand Rapids MI 190,411
Toronto ON 2,503,000
Abbotsford BC 123,865
Milwaukee WI 598,916
Rosemont/Chicago IL 4,230+2,715,000
Hamilton ON 504,560
Rockford IL 150,843
Rochester NY 210,532
Charlotte NC 775,202
Oklahoma City OK 599,199
Cleveland OH 390,928
San Antonio TX 1,383,000
Utica NY 61,822
Des Moines IA 206,688
Cedar Park/Austin TX 57,957+842,592
Like 210 said if you take the greater metro areas into account there aren't many under 100,000 in population. Technically Rosemont is the smallest at 4,230, but its pretty much a part of greater Chicago. Hershey and Glens Falls are next 14,000, but they draw very heavily from their surrounding towns. It would be kinda humorous and amazing to picture well over 2/3rds of Hershey's population showing up to every home game though