You are a resident of Iowa and the state of Iowa will tax all your income.
If you had Illinois tax withheld from your paycheck, you can claim a refund by filing an Illinois tax return, Form IL-1040 and Schedule NR for nonresidents.
Look at last paragraph and have IL employer no longer withhold any IL taxes.
Source of below: https://tax.iowa.gov/iowa-illinois-reciprocal-agreement
Iowa and Illinois have a reciprocal agreement for individual income tax purposes. At this time, Iowa's only income tax reciprocal agreement is with Illinois.
Any wages or salary made by an Iowa resident working in Illinois is taxable only to Iowa and not to Illinois. Any wages or salary made by an Illinois resident working in Iowa is taxable only to Illinois and not to Iowa.
An Iowa resident working for wages or salary in Illinois should complete and file Illinois form IL-W-5-NR “Employee's Statement of Nonresidence in Illinois” with the employer so that the employer will be aware it is appropriate to withhold Iowa income tax. The Iowa resident should also complete an Iowa W-4.
