At the end of 2019, the U. S. had 775,037 licensed amateur radio licensees.  That was an increase of 2.6% from the previous year.  Iowa had 6,582 licensees, and an increase of 254 from the previous year.

Details of the number of amateur radio operators by license type, state, and expiration date may be found at https://sites.google.com/site/amateurradiodata/  

This link gives the data for Iowa  https://sites.google.com/site/amateurradiodata/home/iowa_amateur_radio_data

Note:  Data contained in this link is from the FCC database.  The information is presented by

Keith Greiner, AKØQ